Method for transmitting and receiving physical downlink shared channel in wireless communication system and device supporting same

ABSTRACT

Disclosed are a method of transmitting and receiving a physical downlink shared channel in a wireless communication system and an apparatus supporting the method. More specifically, the method performed by a user equipment may comprise transmitting, to a base station (BS), capability information including first information indicating support for a PDSCH repetition-related operation; receiving, from the BS, an higher layer signal including second information for configuring whether to enable the PDSCH repetition-related operation; receiving Downlink Control Information (DCI) related to reception of a PDSCH repetition from the BS when the second information is configured as enable; and receiving the PDSCH repeatedly from the BS based on the DCI.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/790,642, filed on Feb. 13, 2020, which is a continuation ofInternational Application No. PCT/KR2019/004594, filed on Apr. 16, 2019,which claims the benefit of earlier filing date and right of priority toU.S. Provisional Application No. 62/658,512, filed on Apr. 16, 2018,62/659,095, filed on Apr. 17, 2018, 62/659,674, filed on Apr. 18, 2018,and 62/664,257, filed on Apr. 29, 2018, the contents of which are allhereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method for transmitting and/or reporting a UE'ssupport for repetition of a physical downlink shared channel and anapparatus supporting the method.

BACKGROUND ART

Mobile communication systems have been developed to provide voiceservices, while ensuring activity of users. However, coverage of themobile communication systems has been extended up to data services, aswell as voice service, and currently, an explosive increase in traffichas caused shortage of resources, and since users expect relatively highspeed services, an advanced mobile communication system is required.

Requirements of a next-generation mobile communication system includeaccommodation of explosive data traffic, a significant increase in atransfer rate per user, accommodation of considerably increased numberof connection devices, very low end-to-end latency, and high energyefficiency. To this end, there have been researched various technologiessuch as dual connectivity, massive multiple input multiple output(MIMO), in-band full duplex, non-orthogonal multiple access (NOMA),super wideband, device networking, and the like.

DISCLOSURE Technical Problem

An object of the present specification is to improve reliability ofreceiving a physical downlink shared channel by transmitting and/orreporting a UE's support for repetition of the physical downlink sharedchannel.

Technical problems to be solved by the present invention are not limitedby the above-mentioned technical problems, and other technical problemswhich are not mentioned above can be clearly understood from thefollowing description by those skilled in the art to which the presentinvention pertains.

Technical Solution

The present disclosure proposes a method of receiving a PhysicalDownlink Shared Channel (PDSCH) in a wireless communication system. Amethod performed by a user equipment (UE) may comprise transmitting, toa base station (BS), capability information including first informationindicating support for a PDSCH repetition-related operation; receiving,from the BS, a higher layer signal including second information forconfiguring whether to enable the PDSCH repetition-related operation;receiving, from the BS, Downlink Control Information (DCI) related toreception of a PDSCH repetition when the second information isconfigured as enable; and repeatedly receiving, from the BS the PDSCHbased on the DCI.

Also, in the method of the present disclosure, the capabilityinformation may further include information indicating whetherconfiguration of the number of symbols of a control region through thehigher layer signal is supported.

Also, in the method of the present disclosure, the first information maybe transmitted when configuration of the number of symbols of a controlregion through the higher layer signal is supported.

Also, in the method of the present disclosure, the first information mayindicate whether subframe repetition is supported.

Also, in the method of the present disclosure, the first information mayinclude information indicating whether subframe repetition is supported,information indicating whether slot repetition is supported, andinformation indicating whether subslot repetition is supported,respectively.

Also, in the method of the present disclosure, the PDSCHrepetition-related operation may be an HARQ-less/blind PDSCH repetitionoperation.

Also, a user equipment (UE) receiving a Physical Downlink Shared Channel(PDSCH) in a wireless communication system may comprise a transceivertransmitting and receiving a wireless signal; and a processorfunctionally connected to the transceiver wherein the processor controlsthe UE to transmit, to a BS, capability information including firstinformation indicating support for a PDSCH repetition-related operation;to receive, from the BS, a higher layer signal including secondinformation for configuring whether to enable the PDSCHrepetition-related operation; if the second information is configured asenable, to receive, from the BS, Downlink Control Information (DCI)related to reception of a PDSCH repetition; and to repeatedly receive,from the BS, the PDSCH based on the DCI.

Also, in the UE of the present disclosure, the capability informationmay further include information indicating whether configuration of thenumber of symbols of a control region through the higher layer signal issupported.

Also, in the UE of the present disclosure, the first information may betransmitted when configuration of the number of symbols of a controlregion through the higher layer signal is supported.

Also, in the UE of the present disclosure, the first information mayindicate whether subframe repetition is supported.

Also, in the UE of the present disclosure, the first information mayinclude information indicating whether subframe repetition is supported,information indicating whether slot repetition is supported, andinformation indicating whether subslot repetition is supported,respectively.

Also, in the UE of the present disclosure, the PDSCH repetition-relatedoperation may be an HARQ-less/blind PDSCH repetition operation.

Also, a base station (BS) transmitting a Physical Downlink SharedChannel (PDSCH) in a wireless communication system may comprise atransceiver transmitting and receiving a wireless signal; and aprocessor functionally connected to the transceiver wherein theprocessor controls the BS to receive, from a user equipment (UE),capability information including first information indicating supportfor a PDSCH repetition-related operation; to transmit, to the UE, ahigher layer signal including second information for configuring whetherto enable the PDSCH repetition-related operation; to transmit, to theUE, Downlink Control Information (DCI) related to reception of a PDSCHrepetition when the second information is configured as enable; andrepeatedly to transmit, to the UE, the PDSCH.

Also, in the BS of the present disclosure, the capability informationmay further include information indicating whether configuration of thenumber of symbols of a control region through the higher layer signal issupported.

Also, in the BS of the present disclosure, the first information may bereceived when configuration of the number of symbols of a control regionthrough the higher layer signal is supported.

Advantageous Effects

The present disclosure provides an effect of improving reliability ofreceiving a physical downlink shared channel by transmitting and/orreporting a UE's support for repetition of the physical downlink sharedchannel.

Effects obtainable from the present invention are not limited by theeffects mentioned above, and other effects which are not mentioned abovecan be clearly understood from the following description by thoseskilled in the art to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the present invention and constitute a part of thedetailed description, illustrate embodiments of the present inventionand together with the description serve to explain the principle of thepresent invention.

FIG. 1 illustrates a structure of a radio frame in a wirelesscommunication system to which the present invention is applicable.

FIG. 2 illustrates a resource grid for one downlink slot in a wirelesscommunication system to which the present invention is applicable.

FIG. 3 illustrates a structure of a downlink subframe in a wirelesscommunication system to which the present invention is applicable.

FIG. 4 illustrates a structure of an uplink subframe in a wirelesscommunication system to which the present invention is applicable.

FIG. 5 illustrates an example of an overall structure of a NR system towhich a method proposed by the present specification is applicable.

FIG. 6 illustrates a relation between an uplink frame and a downlinkframe in a wireless communication system to which a method proposed bythe present specification is applicable.

FIG. 7 illustrates an example of a frame structure in a NR system.

FIG. 8 illustrates an example of a resource grid supported in a wirelesscommunication system to which a method proposed by the presentspecification is applicable.

FIG. 9 illustrates examples of a resource grid per antenna port andnumerology to which a method proposed by the present specification isapplicable.

FIG. 10 illustrates an example of a self-contained structure to which amethod proposed by the present specification is applicable.

FIG. 11 illustrates an example in which physical uplink control channel(PUCCH) formats are mapped to PUCCH regions of uplink physical resourceblocks in a wireless communication system to which the present inventionis applicable.

FIG. 12 illustrates a structure of channel quality indicator (CQI)channel in case of a normal cyclic prefix (CP) in a wirelesscommunication system to which the present invention is applicable.

FIG. 13 illustrates a structure of ACK/NACK channel in case of a normalCP in a wireless communication system to which the present invention isapplicable.

FIG. 14 illustrates an example of transport channel processing of anuplink shared channel (UL-SCH) in a wireless communication system towhich the present invention is applicable.

FIG. 15 illustrates an example of signal processing of an uplink sharedchannel that is a transport channel in a wireless communication systemto which the present invention is applicable.

FIG. 16 illustrates an example of generating and transmitting 5 SC-FDMAsymbols during one slot in a wireless communication system to which thepresent invention is applicable.

FIG. 17 illustrates an ACK/NACK channel structure for PUCCH format 3with a normal CP.

FIG. 18 illustrates a problem of reliability reduction in a PDSCHrepetition operation.

FIG. 19 is a flow diagram illustrating an operation method of a UEaccording to the present specification.

FIG. 20 is a flow diagram illustrating an operation method of an basestation according to the present specification.

FIG. 21 illustrates a block diagram of a wireless communication deviceto which methods proposed in the present specification may be applied.

FIG. 22 illustrates a block diagram of a communication device accordingto one embodiment of the present disclosure.

FIG. 23 illustrates one example of an RF module of a wirelesscommunication device to which methods proposed in the presentspecification may be applied.

FIG. 24 illustrates another example of an RF module of a wirelesscommunication device to which methods proposed in the presentspecification may be applied.

MODE FOR INVENTION

Hereafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings. Adetailed description to be disclosed hereinbelow together with theaccompanying drawing is to describe embodiments of the present inventionand not to describe a unique embodiment for carrying out the presentinvention. The detailed description below includes details in order toprovide a complete understanding. However, those skilled in the art knowthat the present invention can be carried out without the details.

In some cases, in order to prevent a concept of the present inventionfrom being ambiguous, known structures and devices may be omitted or maybe illustrated in a block diagram format based on core function of eachstructure and device.

In the specification, a base station means a terminal node of a networkdirectly performing communication with a terminal. In the presentdocument, specific operations described to be performed by the basestation may be performed by an upper node of the base station in somecases. That is, it is apparent that in the network constituted bymultiple network nodes including the base station, various operationsperformed for communication with the terminal may be performed by thebase station or other network nodes other than the base station. A basestation (BS) may be generally substituted with terms such as a fixedstation, Node B, evolved-NodeB (eNB), a base transceiver system (BTS),an access point (AP), and the like. Further, a ‘terminal’ may be fixedor movable and be substituted with terms such as user equipment (UE), amobile station (MS), a user terminal (UT), a mobile subscriber station(MSS), a subscriber station (SS), an advanced mobile station (AMS), awireless terminal (WT), a Machine-Type Communication (MTC) device, aMachine-to-Machine (M2M) device, a Device-to-Device (D2D) device, andthe like.

Hereinafter, a downlink means communication from the base station to theterminal and an uplink means communication from the terminal to the basestation. In the downlink, a transmitter may be a part of the basestation and a receiver may be a part of the terminal. In the uplink, thetransmitter may be a part of the terminal and the receiver may be a partof the base station.

Specific terms used in the following description are provided to helpappreciating the present invention and the use of the specific terms maybe modified into other forms within the scope without departing from thetechnical spirit of the present invention.

The following technology may be used in various wireless access systems,such as code division multiple access (CDMA), frequency divisionmultiple access (FDMA), time division multiple access (TDMA), orthogonalfrequency division multiple access (OFDMA), single carrier-FDMA(SC-FDMA), non-orthogonal multiple access (NOMA), and the like. The CDMAmay be implemented by radio technology universal terrestrial radioaccess (UTRA) or CDMA2000. The TDMA may be implemented by radiotechnology such as Global System for Mobile communications (GSM)/GeneralPacket Radio Service(GPRS)/Enhanced Data Rates for GSM Evolution (EDGE).The OFDMA may be implemented as radio technology such as IEEE802.11(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802-20, E-UTRA(Evolved UTRA),and the like. The UTRA is a part of a universal mobile telecommunicationsystem (UMTS). 3rd generation partnership project (3GPP) long termevolution (LTE) as a part of an evolved UMTS (E-UMTS) using evolved-UMTSterrestrial radio access (E-UTRA) adopts the OFDMA in a downlink and theSC-FDMA in an uplink. LTE-advanced (A) is an evolution of the 3GPP LTE.

The embodiments of the present invention may be based on standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2 whichare the wireless access systems. That is, steps or parts which are notdescribed to definitely show the technical spirit of the presentinvention among the embodiments of the present invention may be based onthe documents. Further, all terms disclosed in the document may bedescribed by the standard document.

3GPP LTE/LTE-A is primarily described for clear description, buttechnical features of the present invention are not limited thereto.

Overview of System

FIG. 1 illustrates a structure of a radio frame in a wirelesscommunication system to which the present invention is applicable.

3GPP LTE/LTE-A supports radio frame structure type 1 applicable tofrequency division duplex (FDD) and radio frame structure Type 2applicable to time division duplex (TDD).

In FIG. 1 , the size of a radio frame in a time domain is represented asa multiple of a time unit of T_s=1/(15000*2048). Downlink and uplinktransmissions are organized into radio frames with a duration ofT_f=307200*T_s=10 ms.

FIG. 1(a) illustrates radio frame structure type 1. The radio framestructure type 1 is applicable to both full duplex FDD and half duplexFDD.

A radio frame consists of 10 subframes. One radio frame consists of 20slots of T_slot=15360*T_s=0.5 ms length, and indexes of 0 to 19 aregiven to the respective slots. One subframe consists of two consecutiveslots in the time domain, and subframe i consists of slot 2i and slot2i+1. A time required to transmit one subframe is referred to as atransmission time interval (TTI). For example, the length of onesubframe may be 1 ms, and the length of one slot may be 0.5 ms.

The uplink transmission and the downlink transmission in the FDD aredistinguished in the frequency domain. Whereas there is no restrictionin the full duplex FDD, a UE cannot transmit and receive simultaneouslyin the half duplex FDD operation.

One slot includes a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in the time domain and includes a pluralityof resource blocks (RBs) in a frequency domain. Since 3GPP LTE usesOFDMA in downlink, OFDM symbols are used to represent one symbol period.The OFDM symbol may be called one SC-FDMA symbol or a symbol period. Theresource block is a resource allocation unit and includes a plurality ofconsecutive subcarriers in one slot.

FIG. 1(b) illustrates frame structure type 2.

The radio frame type 2 consists of two half-frames of 153600*T_s=5 mslength each. Each half-frame consists of five subframes of 30720*T_s=1ms length.

In the frame structure type 2 of a TDD system, uplink-downlinkconfiguration is a rule indicating whether uplink and downlink areallocated (or reserved) to all subframes.

Table 1 represents uplink-downlink configuration.

TABLE 1 Uplink- Downlink-to- Downlink Uplink Switch- config- pointSubframe number uration periodicity 0 1 2 3 4 5 6 7 8 9 0  5 ms D S U UU D S U U U 1  5 ms D S U U D D S U U D 2  5 ms D S U D D D S U D D 3 10ms D S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D DD D D 6  5 ms D S U U U D S U U D

Referring to Table 1, in each subframe of the radio frame, ‘D’represents a subframe for downlink transmission, ‘U’ represents asubframe for uplink transmission, and ‘S’ represents a special subframeconsisting of three types of fields including a downlink pilot time slot(DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS). TheDwPTS is used for an initial cell search, synchronization or channelestimation in a UE. The UpPTS is used for channel estimation in a basestation and uplink transmission synchronization of the UE. The GP is aperiod for removing interference generated in uplink due to multi-pathdelay of a downlink signal between uplink and downlink.

Each subframe i consists of slot 2i and slot 2i+1 ofT_slot=15360*T_s=0.5 ms length each.

The uplink-downlink configuration may be classified into 7 types, and alocation and/or the number of a downlink subframe, a special subframeand an uplink subframe are different for each configuration.

A point of time at which switching from downlink to uplink or switchingfrom uplink to downlink is performed is referred to as a switchingpoint. A switch-point periodicity refers to a period in which switchedpatterns of an uplink subframe and a downlink subframe are equallyrepeated, and both 5 ms and 10 ms switch-point periodicity aresupported. In case of 5 ms downlink-to-uplink switch-point periodicity,the special subframe S exists in every half-frame. In case of 5 msdownlink-to-uplink switch-point periodicity, the special subframe Sexists in a first half-frame only.

In all the configurations, subframes 0 and 5 and a DwPTS are reservedfor downlink transmission only. An UpPTS and a subframe immediatelyfollowing the subframe are always reserved for uplink transmission.

Such uplink-downlink configurations may be known to both the basestation and the UE as system information. The base station may informthe UE of change in an uplink-downlink allocation state of a radio frameby transmitting only indexes of uplink-downlink configurationinformation to the UE each time the uplink-downlink configurationinformation is changed. Furthermore, configuration information is a kindof downlink control information and may be transmitted via a physicaldownlink control channel (PDCCH) like other scheduling information, oris a kind of broadcast information and may be commonly transmitted toall UEs within a cell via a broadcast channel.

Table 2 represents configuration (length of DwPTS/GP/UpPTS) of a specialsubframe.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Normal Extended Normal Normal Special cyclic cycliccyclic cyclic subframe prefix in prefix in prefix in prefix inconfiguration DwPTS uplink uplink DwPTS uplink uplink 0  6592 · T_(s)2192 · T_(s) 2560 T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760· T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s)25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5 6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s)23040 · T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

The structure of a radio frame according to an example of FIG. 1 ismerely an example, and the number of subcarriers included in a radioframe, the number of slots included in a subframe, and the number ofOFDM symbols included in a slot may be variously changed.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin the wireless communication system to which the present invention canbe applied.

Referring to FIG. 2 , one downlink slot includes the plurality of OFDMsymbols in the time domain. Herein, it is exemplarily described that onedownlink slot includes 7 OFDM symbols and one resource block includes 12subcarriers in the frequency domain, but the present invention is notlimited thereto.

Each element on the resource grid is referred to as a resource elementand one resource block includes 12×7 resource elements. The number ofresource blocks included in the downlink slot, NDL is subordinated to adownlink transmission bandwidth.

A structure of the uplink slot may be the same as that of the downlinkslot.

FIG. 3 illustrates a structure of a downlink subframe in the wirelesscommunication system to which the present invention can be applied.

Referring to FIG. 3 , a maximum of three fore OFDM symbols in the firstslot of the sub frame is a control region to which control channels areallocated and residual OFDM symbols is a data region to which a physicaldownlink shared channel (PDSCH) is allocated. Examples of the downlinkcontrol channel used in the 3GPP LTE include a Physical Control FormatIndicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH),a Physical Hybrid-ARQ Indicator Channel (PHICH), and the like.

The PFCICH is transmitted in the first OFDM symbol of the subframe andtransports information on the number (that is, the size of the controlregion) of OFDM symbols used for transmitting the control channels inthe subframe. The PHICH which is a response channel to the uplinktransports an Acknowledgement (ACK)/Not-Acknowledgement (NACK) signalfor a hybrid automatic repeat request (HARQ). Control informationtransmitted through a PDCCH is referred to as downlink controlinformation (DCI). The downlink control information includes uplinkresource allocation information, downlink resource allocationinformation, or an uplink transmission (Tx) power control command for apredetermined terminal group.

The PDCCH may transport A resource allocation and transmission format(also referred to as a downlink grant) of a downlink shared channel(DL-SCH), resource allocation information (also referred to as an uplinkgrant) of an uplink shared channel (UL-SCH), paging information in apaging channel (PCH), system information in the DL-SCH, resourceallocation for an upper-layer (higher-layer) control message such as arandom access response transmitted in the PDSCH, an aggregate oftransmission power control commands for individual terminals in thepredetermined terminal group, a voice over IP (VoIP). A plurality ofPDCCHs may be transmitted in the control region and the terminal maymonitor the plurality of PDCCHs. The PDCCH is constituted by one or anaggregate of a plurality of continuous control channel elements (CCEs).The CCE is a logical allocation wise used to provide a coding ratedepending on a state of a radio channel to the PDCCH. The CCEscorrespond to a plurality of resource element groups. A format of thePDCCH and a bit number of usable PDCCH are determined according to anassociation between the number of CCEs and the coding rate provided bythe CCEs.

The base station determines the PDCCH format according to the DCI to betransmitted and attaches a cyclic redundancy check (CRC) to the controlinformation. The CRC is masked with a unique identifier (referred to asa radio network temporary identifier (RNTI)) according to an owner or apurpose of the PDCCH. In the case of a PDCCH for a specific terminal,the unique identifier of the terminal, for example, a cell-RNTI (C-RNTI)may be masked with the CRC. Alternatively, in the case of a PDCCH forthe paging message, a paging indication identifier, for example, the CRCmay be masked with a paging-RNTI (P-RNTI). In the case of a PDCCH forthe system information, in more detail, a system information block(SIB), the CRC may be masked with a system information identifier, thatis, a system information (SI)-RNTI. The CRC may be masked with a randomaccess (RA)-RNTI in order to indicate the random access response whichis a response to transmission of a random access preamble.

An enhanced PDCCH (EPDCCH) carries UE-specific signaling. The EPDCCH islocated in a physical resource block (PRB) that is configured to be UEspecific. In other words, as described above, the PDCCH may betransmitted in up to first three OFDM symbols in a first slot of asubframe, but the EPDCCH may be transmitted in a resource region otherthan the PDCCH. A time (i.e., symbol) at which the EPDCCH starts in thesubframe may be configured to the UE via higher layer signaling (e.g.,RRC signaling, etc.).

The EPDCCH may carry a transport format, resource allocation and HARQinformation related to DL-SCH, a transport format, resource allocationand HARQ information related to UL-SCH, resource allocation informationrelated to sidelink shared channel (SL-SCH) and physical sidelinkcontrol channel (PSCCH), etc. Multiple EPDCCHs may be supported, and theUE may monitor a set of EPCCHs.

The EPDCCH may be transmitted using one or more consecutive enhancedCCEs (ECCEs), and the number of ECCEs per EPDCCH may be determined foreach EPDCCH format.

Each ECCE may consist of a plurality of enhanced resource element groups(EREGs). The EREG is used to define mapping of the ECCE to the RE. Thereare 16 EREGs per PRB pair. All REs except the RE carrying the DMRS ineach PRB pair are numbered from 0 to 15 in increasing order of thefrequency and then in increasing order of time.

The UE may monitor a plurality of EPDCCHs. For example, one or twoEPDCCH sets may be configured in one PRB pair in which the UE monitorsEPDCCH transmission.

Different coding rates may be implemented for the EPCCH by combiningdifferent numbers of ECCEs. The EPCCH may use localized transmission ordistributed transmission, and hence, the mapping of ECCE to the RE inthe PRB may vary.

FIG. 4 illustrates a structure of an uplink subframe in the wirelesscommunication system to which the present invention can be applied.

Referring to FIG. 4 , the uplink subframe may be divided into thecontrol region and the data region in a frequency domain. A physicaluplink control channel (PUCCH) transporting uplink control informationis allocated to the control region. A physical uplink shared channel(PUSCH) transporting user data is allocated to the data region. Oneterminal does not simultaneously transmit the PUCCH and the PUSCH inorder to maintain a single carrier characteristic.

A resource block (RB) pair in the subframe are allocated to the PUCCHfor one terminal. RBs included in the RB pair occupy differentsubcarriers in two slots, respectively. The RB pair allocated to thePUCCH frequency-hops in a slot boundary.

The following invention proposed by the present specification can beapplied to a 5G NR system (or device) as well as a LTE/LTE-A system (ordevice).

Communication of the 5G NR system is described below with reference toFIGS. 5 to 10 .

The 5G NR system defines enhanced mobile broadband (eMBB), massivemachine type communications (mMTC), ultra-reliable and low latencycommunications (URLLC), and vehicle-to-everything (V2X) based on usagescenario (e.g., service type).

A 5G NR standard is divided into standalone (SA) and non-standalone(NSA) depending on co-existence between a NR system and a LTE system.

The 5G NR system supports various subcarrier spacings and supportsCP-OFDM in the downlink and CP-OFDM and DFT-s-OFDM (SC-OFDM) in theuplink.

Embodiments of the present invention can be supported by standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2 whichare the wireless access systems. That is, steps or parts in embodimentsof the present invention which are not described to clearly show thetechnical spirit of the present invention can be supported by thestandard documents. Further, all terms disclosed in the presentdisclosure can be described by the standard document.

As smartphones and Internet of Things (IoT) terminals spread rapidly, anamount of information exchanged through a communication network isincreasing. Hence, it is necessary to consider an environment (e.g.,enhanced mobile broadband communication) that provides faster servicesto more users than the existing communication system (or existing radioaccess technology) in the next generation wireless access technology.

To this end, a design of a communication system considering machine typecommunication (MTC) that provides services by connecting multipledevices and objects is being discussed. In addition, a design of acommunication system (e.g., ultra-reliable and low latency communication(URLLC) considering a service and/or a terminal sensitive to reliabilityand/or latency of communication is also being discussed.

Hereinafter, in the present specification, for convenience ofexplanation, the next generation radio access technology is referred toas NR (new RAT, radio access technology), and a wireless communicationsystem to which the NR is applied is referred to as an NR system.

Definition of NR System Related Terms

eLTE eNB: The eLTE eNB is the evolution of eNB that supportsconnectivity to EPC and NGC.

gNB: A node which supports the NR as well as connectivity to NGC.

New RAN: A radio access network which supports either NR or E-UTRA orinterfaces with the NGC.

Network slice: A network slice is a network defined by the operatorcustomized to provide an optimized solution for a specific marketscenario which demands specific requirements with end-to-end scope.

Network function: A network function is a logical node within a networkinfrastructure that has well-defined external interfaces andwell-defined functional behavior.

NG-C: A control plane interface used on NG2 reference points between newRAN and NGC.

NG-U: A user plane interface used on NG3 reference points between newRAN and NGC.

Non-standalone NR: A deployment configuration where the gNB requires anLTE eNB as an anchor for control plane connectivity to EPC, or requiresan eLTE eNB as an anchor for control plane connectivity to NGC.

Non-standalone E-UTRA: A deployment configuration where the eLTE eNBrequires a gNB as an anchor for control plane connectivity to NGC.

User plane gateway: A termination point of NG-U interface.

FIG. 5 illustrates an example of an overall structure of a NR system towhich a method proposed by the present specification is applicable.

Referring to FIG. 5 , an NG-RAN consists of gNBs that provide an NG-RAuser plane (new AS sublayer/PDCP/RLC/MAC/PHY) and control plane (RRC)protocol terminations for a user equipment (UE).

The gNBs are interconnected with each other by means of an Xn interface.

The gNBs are also connected to an NGC by means of an NG interface.

More specifically, the gNBs are connected to an access and mobilitymanagement function (AMF) by means of an N2 interface and to a userplane function (UPF) by means of an N3 interface.

NR (New Rat) Numerology and Frame Structure

In a NR system, multiple numerologies can be supported. A numerology maybe defined by a subcarrier spacing and a cyclic prefix (CP) overhead.Multiple subcarrier spacings can be derived by scaling a basicsubcarrier spacing by an integer N (or μ). Further, although it isassumed not to use a very low subcarrier spacing at a very high carrierfrequency, the numerology used can be selected independently of afrequency band.

In the NR system, various frame structures according to the multiplenumerologies can be supported.

Hereinafter, an orthogonal frequency division multiplexing (OFDM)numerology and a frame structure which may be considered in the NRsystem will be described.

Multiple OFDM numerologies supported in the NR system may be defined asin Table 3.

TABLE 3 μ Δf = 2^(μ) · 15 [kHz] Cyclic prefix 0 15 Normal 1 30 Normal 260 Normal, Extended 3 120 Normal 4 240 Normal

In regard to a frame structure in the NR system, a size of variousfields in a time domain is expressed as a multiple of a time unit ofT_(s)=1/(Δf_(max)·N_(f)), where Δf_(max)=480·10³ and N_(f)=4096.Downlink and uplink transmissions are organized into radio frames with aduration of T_(f)=(Δf_(max)N_(f)/100)·T_(s)=10 ms. Here, the radio frameconsists of ten subframes each having a duration ofT_(sf)=(Δf_(max)N_(f)/1000)·T_(s)=1 ms. In this case, there may be a setof frames in the uplink and a set of frames in the downlink. FIG. 6illustrates a relation between an uplink frame and a downlink frame in awireless communication system to which a method proposed by the presentspecification is applicable.

As illustrated in FIG. 6 , uplink frame number i for transmission from auser equipment (UE) shall start T_(TA)=N_(TA)T_(s) before the start of acorresponding downlink frame at the corresponding UE.

Regarding the numerology μ, slots are numbered in increasing order ofn_(s) ^(μ)∈{0, . . . , N_(subframe) ^(slots,μ)−1} within a subframe andare numbered in increasing order of n_(s,f) ^(μ)∈{0, . . . , N_(frame)^(slots,μ)−1} within a radio frame. One slot consists of consecutiveOFDM symbols of N_(symb) ^(μ), and N_(symb) ^(μ) is determined dependingon a numerology used and slot configuration. The start of slots n_(s)^(μ) in a subframe is aligned in time with the start of OFDM symbolsn_(s) ^(μ)N_(symb) ^(μ) in the same subframe.

Not all UEs are able to transmit and receive at the same time, and thismeans that not all OFDM symbols in a downlink slot or an uplink slot areavailable to be used.

Table 4 represents the number N_(symb) ^(slot) of OFDM symbols per slot,the number N_(slot) ^(frame,μ) of slots per radio frame, and the numberN_(slot) ^(subframe,μ) of slots per subframe in a normal CP. Table 5represents the number of OFDM symbols per slot, the number of slots perradio frame, and the number of slots per subframe in an extended CP.

TABLE 4 μ N_(symb) ^(slot) N_(slot) ^(frame, μ) N_(slot) ^(subframe, μ)0 14 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16

TABLE 5 μ N_(symb) ^(slot) N_(slot) ^(frame, μ) N_(slot) ^(subframe, μ)2 12 40 4

FIG. 7 illustrates an example of a frame structure in a NR system. FIG.7 is merely for convenience of explanation and does not limit the scopeof the present invention. In Table 5, in case of μ=2, i.e., as anexample in which a subcarrier spacing (SCS) is 60 kHz, one subframe (orframe) may include four slots with reference to Table 4, and onesubframe={1, 2, 4} slots shown in FIG. 3 , for example, the number ofslot(s) that may be included in one subframe may be defined as in Table2.

Further, a mini-slot may consist of 2, 4, or 7 symbols, or may consistof more symbols or less symbols.

In regard to physical resources in the NR system, an antenna port, aresource grid, a resource element, a resource block, a carrier part,etc. may be considered.

Hereinafter, the above physical resources that can be considered in theNR system are described in more detail.

First, in regard to an antenna port, the antenna port is defined so thata channel over which a symbol on an antenna port is conveyed can beinferred from a channel over which another symbol on the same antennaport is conveyed. When large-scale properties of a channel over which asymbol on one antenna port is conveyed can be inferred from a channelover which a symbol on another antenna port is conveyed, the two antennaports may be regarded as being in a quasi co-located or quasico-location (QC/QCL) relation. Here, the large-scale properties mayinclude at least one of delay spread, Doppler spread, frequency shift,average received power, and received timing.

FIG. 8 illustrates an example of a resource grid supported in a wirelesscommunication system to which a method proposed by the presentspecification is applicable.

Referring to FIG. 8 , a resource grid consists of N_(RB) ^(μ)N_(sc)^(RB) subcarriers on a frequency domain, each subframe consisting of14·2μ OFDM symbols, but the present invention is not limited thereto.

In the NR system, a transmitted signal is described by one or moreresource grids, consisting of N_(RB) ^(μ)N_(sc) ^(RB) subcarriers, and2^(μ)N_(symb) ^((μ)) OFDM symbols, where N_(RB) ^(μ)≤N_(RB) ^(max,μ).N_(RB) ^(max,μ) denotes a maximum transmission bandwidth and may changenot only between numerologies but also between uplink and downlink.

In this case, as illustrated in FIG. 9 , one resource grid may beconfigured per numerology μ and antenna port p.

FIG. 9 illustrates examples of a resource grid per antenna port andnumerology to which a method proposed by the present specification isapplicable.

Each element of the resource grid for the numerology μ and the antennaport p is called a resource element and is uniquely identified by anindex pair (k,l), where k=0, . . . , N_(RB) ^(μ)N_(sc) ^(RB)−1 is anindex on a frequency domain, and l=0, . . . , 2^(μ)N_(symb) ^((μ))−1refers to a location of a symbol in a subframe. The index pair (k,l) isused to refer to a resource element in a slot, where l=0, . . . ,N_(symb) ^(μ)−1.

The resource element (k,l) for the numerology μ and the antenna port pcorresponds to a complex value a_(k,l) ^((p,μ)). When there is no riskfor confusion or when a specific antenna port or numerology is notspecified, the indexes p and μ may be dropped, and as a result, thecomplex value may be a_(k,l) ^((p)) or a_(k,l) .

Further, a physical resource block is defined as N_(sc) ^(RB)=12consecutive subcarriers in the frequency domain.

Point A serves as a common reference point of a resource block grid andmay be obtained as follows.

-   -   offsetToPointA for PCell downlink represents a frequency offset        between the point A and a lowest subcarrier of a lowest resource        block that overlaps a SS/PBCH block used by the UE for initial        cell selection, and is expressed in units of resource blocks        assuming 15 kHz subcarrier spacing for FR1 and 60 kHz subcarrier        spacing for FR2;    -   absoluteFrequencyPointA represents frequency-location of the        point A expressed as in absolute radio-frequency channel number        (ARFCN).

The common resource blocks are numbered from 0 and upwards in thefrequency domain for subcarrier spacing configuration μ.

The center of subcarrier 0 of common resource block 0 for the subcarrierspacing configuration μ coincides with ‘point A’. A common resourceblock number n_(CRB) ^(μ) in the frequency domain and resource elements(k, l) for the subcarrier spacing configuration may be given by thefollowing Equation 1.

$\begin{matrix}{n_{CRB}^{\mu} = \left\lfloor \frac{k}{N_{sc}^{RB}} \right\rfloor} & \left\lbrack {{Equation}1} \right\rbrack\end{matrix}$

Here, k may be defined relative to the point A so that k=⁰ correspondsto a subcarrier centered around the point A. Physical resource blocksare defined within a bandwidth part (BWP) and are numbered from 0 toN_(BWP,j) ^(size)−1, where i is No. of the BWP. A relation between thephysical resource block n_(PRB) in BWP i and the common resource blockn_(CRB) may be given by the following Equation 2.n _(CRB) =n _(PRB) +N _(BWP,i) ^(start)  [Equation 2]

Here, N_(BWP,i) ^(start) may be the common resource block where the BWPstarts relative to the common resource block 0.

Self-Contained Structure

A time division duplexing (TDD) structure considered in the NR system isa structure in which both uplink (UL) and downlink (DL) are processed inone slot (or subframe). The structure is to minimize a latency of datatransmission in a TDD system and may be referred to as a self-containedstructure or a self-contained slot.

FIG. 10 illustrates an example of a self-contained structure to which amethod proposed by the present specification is applicable. FIG. 10 ismerely for convenience of explanation and does not limit the scope ofthe present invention.

Referring to FIG. 10 , as in legacy LTE, it is assumed that onetransmission unit (e.g., slot, subframe) consists of 14 orthogonalfrequency division multiplexing (OFDM) symbols.

In FIG. 10 , a region 1002 means a downlink control region, and a region1004 means an uplink control region. Further, regions (i.e., regionswithout separate indication) other than the region 1002 and the region1004 may be used for transmission of downlink data or uplink data.

That is, uplink control information and downlink control information maybe transmitted in one self-contained slot. On the other hand, in case ofdata, uplink data or downlink data is transmitted in one self-containedslot.

When the structure illustrated in FIG. 10 is used, in one self-containedslot, downlink transmission and uplink transmission may sequentiallyproceed, and downlink data transmission and uplink ACK/NACK receptionmay be performed.

As a result, if an error occurs in the data transmission, time requireduntil retransmission of data can be reduced. Hence, the latency relatedto data transfer can be minimized.

In the self-contained slot structure illustrated in FIG. 10 , a basestation (e.g., eNodeB, eNB, gNB) and/or a user equipment (UE) (e.g.,terminal) require a time gap for a process for converting a transmissionmode into a reception mode or a process for converting a reception modeinto a transmission mode. In regard to the time gap, if uplinktransmission is performed after downlink transmission in theself-contained slot, some OFDM symbol(s) may be configured as a guardperiod (GP).

Physical Uplink Control Channel (PUCCH)

Uplink control information (UCI) transmitted on a PUCCH may includescheduling request (SR), HARQ ACK/NACK information, and downlink channelmeasurement information.

The HARQ ACK/NACK information may be produced depending on whetherdecoding of downlink data packet on a PDSCH is successful or not. In theexisting wireless communication system, one ACK/NACK bit is transmittedin case of single codeword downlink transmission while two ACK/NACK bitsare transmitted in case of two codeword downlink transmissions.

The channel measurement information refers to feedback informationrelated to a multiple input multiple output (MIMO) scheme and mayinclude a channel quality indicator (CQI), a precoding matrix index(PMI), and a rank indicator (RI). The channel measurement informationmay collectively be referred to as a CQI.

20 bits per subframe may be used for the CQI transmission.

The PUCCH may be modulated by using a binary phase shift keying (BPSK)scheme and a quadrature phase shift keying (QPSK) scheme. Controlinformation for a plurality of UEs may be transmitted on the PDCCH. Incase of performing code division multiplexing (CDM) to distinguishsignals of the respective UEs, a length-12 constant amplitude zeroautocorrelation (CAZAC) sequence is mostly used. Since the CAZACsequence has characteristics of maintaining a predetermined amplitude ina time domain and a frequency domain, the CAZAC has properties suitableto increase coverage by reducing a peak-to-average power ratio (PAPR) ora cubic metric (CM) of the UE. In addition, the ACK/NACK information fordownlink data transmission transmitted on the PDCCH is covered by usingan orthogonal sequence or an orthogonal cover (OC).

Further, control information transmitted on the PUCCH may bedistinguished using a cyclically shifted sequence each having adifferent cyclic shift (CS) value. The cyclically shifted sequence maybe produced by cyclically shifting a base sequence by as much as aspecific cyclic shift (CS) amount. The specific CS amount is indicatedby a CS index. The number of available cyclic shifts may vary dependingon the delay spread of a channel. Various kinds of sequences may be usedas the base sequence, and the CAZAC sequence described above is anexample.

An amount of control information that the UE can transmit in onesubframe may be determined depending on the number of SC-FDMA symbols(i.e., SC-FDMA symbols except SC-FDMA symbols used for reference signal(RS) transmission for coherent detection of the PUCCH), that can be usedin the transmission of the control information.

In the 3GPP LTE system, the PUCCH is defined as a total of sevendifferent formats depending on transmitted control information, amodulation scheme, an amount of control information, etc., andattributes of uplink control information (UCI) transmitted according toeach PUCCH format may be summarized as in the following Table 6.

TABLE 6 PUCCH Format Uplink Control Information(UCI) Format 1 SchedulingRequest (SR) (unmodulated waveform) Format 1a 1-bit HARQ ACK/NACKwith/without SR Format 1b 2-bit HARQ ACK/NACK with/without SR Format 2CQI (20 coded bits) Format 2 CQI and 1- or 2-bit HARQ ACK/NACK (20 bits)for extended CP only Format 2a CQI and 1-bit HARQ ACK/ NACK (20 + 1coded bits) Format 2b CQI and 2-bit HARQ ACK/ NACK (20 + 2 coded bits)

PUCCH format 1 is used for single transmission of SR. In case of singletransmission of SR, an unmodulated waveform is applied, which will bedescribed below in detail. PUCCH format 1a or 1b is used fortransmission of HARQ ACK/NACK. In case of single transmission of HARQACK/NACK in a random subframe, PUCCH format 1a or 1b may be used.Alternatively, the HARQ ACK/NACK and the SR may be transmitted in thesame subframe using the PUCCH format 1a or 1b.

PUCCH format 2 is used for transmission of a CQI, and PUCCH format 2a or2b is used for transmission of the CQI and the HARQ ACK/NACK.

In case of an extended CP, the PUCCH format 2 may also be used fortransmission of the CQI and the HARQ ACK/NACK.

FIG. 11 illustrates an example in which PUCCH formats are mapped toPUCCH regions of uplink physical resource blocks in a wirelesscommunication system to which the present invention is applicable.

In FIG. 11 , N_(RB) ^(UL) represents the number of resource blocks inthe uplink, and 0, 1, . . . , N_(RB) ^(UL)−1 refers to No. of s physicalresource block. Basically, the PUCCH is mapped to both edges of anuplink frequency block. As illustrated in FIG. 11 , the PUCCH format2/2a/2b is mapped to a PUCCH region marked by m=0, 1, which mayrepresent that the PUCCH format 2/2a/2b is mapped to resource blockslocated at band edges. In addition, the PUCCH format 2/2a/2b and thePUCCH format 1/1a/1b are mixedly mapped to the PUCCH region marked bym=2. Next, the PUCCH format 1/1a/1b may be mapped to a PUCCH regionmarked by m=3, 4, 5. The number N_(RB) ⁽²⁾ of PUCCH RBs available foruse by the PUCCH format 2/2a/2b may be indicated to the UEs in a cell bybroadcasting signaling.

The PUCCH format 2/2a/2b is described. The PUCCH format 2/2a/2b is acontrol channel used to transmit channel measurement feedbacks CQI, PMI,and RI.

A periodicity and a frequency unit (or a frequency resolution) to beused to report the channel measurement feedback (hereinafter,collectively referred to as CQI information) may be controlled by thebase station. Periodic CQI reporting and aperiodic CQI reporting in atime domain can be reported. The PUCCH format 2 may be used for theperiodic CQI reporting only, and the PUSCH may be used for the aperiodicCQI reporting. In case of the aperiodic CQI reporting, the base stationmay instruct the UE to send an individual CQI report embedded into aresource which is scheduled for uplink data transmission.

FIG. 12 illustrates a structure of CQI channel in case of a normal CP ina wireless communication system to which the present invention isapplicable.

Among SC-FDMA symbols 0 to 6 of one slot, SC-FDMA symbols 1 and 5(second and sixth symbols) may be used for transmission of demodulationreference signal (DMRS), and the CQI information may be transmitted inthe remaining SC-FDMA symbols. In case of the extended CP, one SC-FDMAsymbol (SC-FDMA symbol 3) is used for the DMRS transmission.

In the PUCCH format 2/2a/2b, the modulation by the CAZAC sequence issupported, and a QPSK modulated symbol is multiplied by the length-12CAZAC sequence. A cyclic shift (CS) of the sequence is changed betweensymbols and slots. An orthogonal covering is used for the DMRS.

The reference signal (DMRS) is carried on two SC-FDMA symbols which areseparated from each other at an interval of three SC-FDMA symbols amongseven SC-FDMA symbols included in one slot, and the CQI information iscarried on the remaining five SC-FDMA symbols. The use of two RSs in oneslot is to support a high speed UE. Further, the respective UEs aredistinguished using a cyclic shift (CS) sequence. CQI informationsymbols are modulated and transmitted to all the SC-FDMA symbols, andthe SC-FDMA symbol is composed of one sequence. That is, the UEmodulates the CQI and transmits the modulated CQI to each sequence.

The number of symbols which can be transmitted in one TTI is 10, and themodulation of the CQI information is also determined up to the QPSK.Since a 2-bit CQI value can be carried in case of using the QPSK mappingfor the SC-FDMA symbol, a 10-bit CQI value can be carried on one slot.Thus, a CQI value of maximum 20 bits can be carried in one subframe. Afrequency domain spreading code is used to spread the CQI information ina frequency domain.

As the frequency domain spreading code, length-12 CAZAC sequence (e.g.,ZC sequence) may be used. Each control channel may be distinguished byapplying the CAZAC sequence having a different cyclic shift value. AnIFFT is performed on frequency domain spreading CQI information.

The 12 equally-spaced cyclic shifts may allow 12 different UEs to beorthogonally multiplexed on the same PUCCH RB. In case of a normal CP, aDMRS sequence on the SC-FDMA symbol 1 and 5 (on the SC-FDMA symbol 3 incase of an extended CP) is similar to a CQI signal sequence on thefrequency domain, but the modulation like the CQI information is notapplied.

The UE may be semi-statically configured by higher layer signaling toreport periodically different CQI, PMI, and RI types on PUCCH resourcesindicated as PUCCH resource indexes (

,

,

) Here, the PUCCH resource index (

) is information indicating a PUCCH region used for the PUCCH format2/2a/2b transmission and a cyclic shift (CS) value to be used.

PUCCH Channel Structure

PUCCH formats 1a and 1b are described.

In the PUCCH format 1a/1b, a symbol modulated using a BPSK or QPSKmodulation scheme is multiplied by length-12 CAZAC sequence. Forexample, the result of multiplying length-N CAZAC sequence r(n) (wheren=0, 1, 2, . . . , N−1) by a modulation symbol d(0) is y(0), y(1), y(2),. . . , y(N−1). The symbols y(0), y(1), y(2), . . . , y(N−1) may bereferred to as a block of symbols. After the CAZAC sequence ismultiplied by the modulation symbol, the block-wise spreading using anorthogonal sequence is applied.

A length-4 Hadamard sequence is used for normal ACK/NACK information,and a length-3 discrete fourier transform (DFT) sequence is used forshortened ACK/NACK information and a reference signal.

A length-2 Hadamard sequence is used for the reference signal in case ofan extended CP.

FIG. 13 illustrates a structure of ACK/NACK channel in case of a normalCP in a wireless communication system to which the present invention isapplicable.

More specifically, FIG. 13 illustrates an example of a PUCCH channelstructure for HARQ ACK/NACK transmission without CQI.

A reference signal (RS) is carried on three consecutive SC-FDMA symbolsin the middle of seven SC-FDMA symbols included in one slot, and anACK/NACK signal is carried on the remaining four SC-FDMA symbols.

In case of an extended CP, the RS may be carried on two consecutivesymbols in the middle. The number and location of symbols used for theRS may vary depending on a control channel, and the number and locationof symbols used for the ACK/NACK signal related may be changedaccordingly.

Both 1-bit and 2-bit acknowledgement information (in a state of notbeing scrambled) may be expressed as a single HARQ ACK/NACK modulationsymbol using the BPSK and QPSK modulation schemes, respectively.Positive acknowledgement (ACK) may be encoded as ‘1’, and negative ACK(NACK) may be encoded as ‘0’.

When a control signal is transmitted in an allocated bandwidth,two-dimensional spreading is applied to increase a multiplexingcapacity. That is, frequency domain spreading and time domain spreadingare simultaneously applied to increase the number of UEs or the numberof control channels that can be multiplexed.

In order to spread an ACK/NACK signal in the frequency domain, afrequency domain sequence is used as a base sequence. As the frequencydomain sequence, a Zadoff-Chu (ZC) sequence which is a kind of CAZACsequence may be used. For example, multiplexing of different UEs ordifferent control channels can be applied by applying different cyclicshifts (CS) to the ZC sequence which is the base sequence. The number ofCS resources supported in SC-FDMA symbols for PUCCH RBs for the HARQACK/NACK transmission is configured by a cell-specific higher layersignaling parameter shirt Δ_(shift) ^(PUCCH).

The frequency domain spreading ACK/NACK signal is spread in a timedomain using an orthogonal spreading code. A Walsh-Hadamard sequence ora DFT sequence may be used as the orthogonal spreading code. Forexample, the ACK/NACK signal may be spread using length-4 orthogonalsequences (w0, w1, w2, w3) for four symbols. An RS is also spreadthrough length-3 or length-2 orthogonal sequence. This is referred to asorthogonal covering (OC).

As described above, multiple UEs may be multiplexed in a code divisionmultiplexing (CDM) method using CS resources in the frequency domain andOC resources in the time domain. That is, ACK/NACK information and a RSof a large number of UEs may be multiplexed on the same PUCCH RB.

As to the time domain spreading CDM, the number of spreading codessupported for the ACK/NACK information is limited by the number of RSsymbols. That is, since the number of SC-FDMA symbols for RStransmission is less than the number of SC-FDMA symbols for ACK/NACKinformation transmission, a multiplexing capacity of the RS is less thana multiplexing capacity of the ACK/NACK information.

For example, in case of the normal CP, the ACK/NACK information may betransmitted on four symbols, and not four but three orthogonal spreadingcodes may be used for the ACK/NACK information. This is because thenumber of RS transmission symbols is limited to three, and threeorthogonal spreading codes only may be used for the RS.

If three symbols in one slot are used for the RS transmission and foursymbols are used for the ACK/NACK information transmission in a subframeof the normal CP, for example, if six cyclic shifts (CSs) in thefrequency domain and three orthogonal covering (OC) resources in thetime domain can be used, HARQ acknowledgement from a total of 18different UEs may be multiplexed within one PUCCH RB. If two symbols inone slot are used for the RS transmission and four symbols are used forthe ACK/NACK information transmission in a subframe of the extended CP,for example, if six cyclic shifts (CSs) in the frequency domain and twoorthogonal covering (OC) resources in the time domain can be used, HARQacknowledgement from a total of 12 different UEs may be multiplexed inone PUCCH RB.

Next, the PUCCH format 1 is described. A scheduling request (SR) istransmitted in such a manner that the UE is requested to be scheduled oris not request. A SR channel reuses an ACK/NACK channel structure in thePUCCH format 1a/1b, and is configured in an on-off keying (OOK) methodbased on an ACK/NACK channel design. In the SR channel, a referencesignal is not transmitted. Thus, length-7 sequence is used in the normalCP, and length-6 sequence is used in the extended CP. Different cyclicshifts or orthogonal covers may be allocated for the SR and theACK/NACK. That is, the UE transmits HARQ ACK/NACK on resources allocatedfor the SR for the purpose of positive SR transmission. The UE transmitsHARQ ACK/NACK on resources allocated for the ACK/NACK for the purpose ofnegative SR transmission.

Next, an enhanced-PUCCH (e-PUCCH) format is described. The e-PUCCHformat may correspond to PUCCH format 3 of the LTE-A system. A blockspreading scheme may be applied to the ACK/NACK transmission using thePUCCH format 3.

PUCCH Piggybacking in Rel-8 LTE

FIG. 14 illustrates an example of transport channel processing of anUL-SCH in a wireless communication system to which the present inventionis applicable.

In the 3GPP LTE system (=E-UTRA, Rel. 8), in case of the UL, forefficient utilization of a power amplifier of a terminal,peak-to-average power ratio (PAPR) characteristics or cubic metric (CM)characteristics that affect a performance of the power amplifier areconfigured so that good single carrier transmission is maintained. Thatis, in the existing LTE system, the good single carrier characteristicscan be maintained by maintaining single carrier characteristics of datato be transmitted through DFT-precoding in case of the PUSCHtransmission, and transmitting information carried on a sequence withthe single carrier characteristic in case of the PUCCH transmission.However, when DFT-precoded data is non-consecutively allocated to afrequency axis or the PUSCH and the PUCCH are simultaneouslytransmitted, the single carrier characteristics are degraded. Thus, asillustrated in FIG. 8 , when the PUSCH is transmitted in the samesubframe as the PUCCH transmission, uplink control information (UCI) tobe transmitted to the PUCCH for the purpose of maintaining the singlecarrier characteristics is transmitted (piggyback) together with thedata via the PUSCH.

As described above, because the PUCCH and the PUSCH cannot besimultaneously transmitted in the existing LTE terminal, the existingLTE terminal uses a method that multiplexes uplink control information(UCI) (CQI/PMI, HARQ-ACK, RI, etc.) to the PUSCH region in a subframe inwhich the PUSCH is transmitted.

For example, when a channel quality indicator (CQI) and/or a precodingmatrix indicator (PMI) needs to be transmitted in a subframe allocatedto transmit the PUSCH, UL-SCH data and the CQI/PMI are multiplexedbefore DFT-spreading to transmit both control information and data. Inthis case, the UL-SCH data performs rate-matching considering CQI/PMIresources. Further, a scheme is used, in which control information suchas HARQ ACK and RI punctures the UL-SCH data and is multiplexed to thePUSCH region.

FIG. 15 illustrates an example of signal processing of an uplink sharedchannel that is a transport channel in a wireless communication systemto which the present invention is applicable.

Hereinafter, signal processing of an uplink shared channel (hereinafter,referred to as “UL-SCH”) may be applied to one or more transportchannels or control information types.

Referring to FIG. 15 , the UL-SCH transfers data to a coding unit in theform of a transport block (TB) once every transmission time interval(TTI).

CRC parity bits p₀, p₁, p₂, p₃, . . . , p_(L)−1 are attached to bits a₀,a₁, a₂, a₃, . . . , a_(A−1) of a transport block transferred from theupper layer (higher layer). In this instance, A denotes a size of thetransport block, and L denotes the number of parity bits. Input bits, towhich the CRC is attached, are denoted by b₀, b₁, b₂, b₃, . . . ,b_(B−1). In this instance, B denotes the number of bits of the transportblock including the CRC.

b₀, b₁, b₂, b₃, . . . , b_(B−1) are segmented into multiple code blocks(CBs) according to the size of the TB, and the CRC is attached to themultiple segmented CBs. Bits after the code block segmentation and theCRC attachment are denoted by c_(r0), c_(r1), c_(r2), c_(r3), . . . ,c_(r(K) _(r) ⁻¹⁾. Here, r represents No. (r=0, . . . , C−1) of the codeblock, and Kr represents the number of bits depending on the code blockr. Further, C represents the total number of code blocks.

Subsequently, channel coding is performed. Output bits after the channelcoding are denoted by d_(r0) ^((i)), d_(r1) ^((i)), d_(r2) ^((i)),d_(r3) ^((i)), . . . , d_(r(D) _(r) ⁻¹⁾ ^((i)). In this instance, irepresents a coded stream index and may have a value of 0, 1, or 2. Drrepresents the number of bits of an i-th coded stream for a code blockr. r represents a code block number (r=0, . . . , C−1), and C representsthe total number of code blocks. Each code block may be coded by turbocoding.

Subsequently, rate matching is performed. Bits after the rate matchingare denoted by e_(r0), e_(r1), e_(r2), e_(r3), . . . , e_(r(E) _(r) ⁻¹⁾.In this case, r represents the code block number (r=0, . . . , C−1), andC represents the total number of code blocks. Er represents the numberof rate-matched bits of a r-th code block.

Subsequently, concatenation between the code blocks is performed again.Bits after the concatenation of the code blocks is performed are denotedby f₀, f₁, f₂, f₃, . . . , f_(G−1). In this instance, G represents thetotal number of bits coded for transmission, and when the controlinformation is multiplexed with the UL-SCH, the number of bits used forthe transmission of the control information is not included.

When the control information is transmitted on the PUSCH, channel codingof CQI/PMI, RI, and ACK/NACK which are the control information isindependently performed. Because different coded symbols are allocatedfor the transmission of each control information, each controlinformation has a different coding rate.

In time division duplex (TDD), an ACK/NACK feedback mode supports twomodes of ACK/NACK bundling and ACK/NACK multiplexing by higher layerconfiguration. ACK/NACK information bit for the ACK/NACK bundlingconsists of 1 bit or 2 bits, and ACK/NACK information bit for theACK/NACK multiplexing consists of between 1 bit and 4 bits.

After the concatenation between the code blocks, coded bits f₀, f₁, f₂,f₃, . . . , f_(G−1) of the UL-SCH data and coded bits q₀, q₁, q₂, q₃, .. . , q_(N) _(L) _(·Q) _(CQI) ⁻¹ of the CQI/PMI are multiplexed. Theresult of multiplexing the data and the CQI/PMI is denoted by g₀, g₁,g₂, g₃, . . . , g_(H′−1). In this instance, g_(i) (i=0, . . . , H′−1)represents a column vector with a length of (Q_(m)·N_(L)),H=(G+N_(L)·Q_(CQI)), and H′=H/(N_(L)·Q_(m)). N_(L) represents the numberof layers mapped to a UL-SCH transport block, and H represents the totalnumber of coded bits allocated, for the UL-SCH data and the CQI/PMIinformation, to N_(L) transport layers to which the transport block ismapped.

Subsequently, multiplexed data and CQI/PMI, separately channel-coded RI,and ACK/NACK are channel-interleaved to generate an output signal.

PDCCH Assignment Procedure

A plurality of PDCCHs may be transmitted within one subframe. That is, acontrol region of one subframe consists of a plurality of CCEs havingindexes 0 to N_(CCE,k)−1, where N_(CCE,k) denotes the total number ofCCEs in a control region of a k-th subframe. The UE monitors a pluralityof PDCCHs in every subframe. Here, the monitoring means that the UEattempts the decoding of each PDCCH depending on a monitored PDCCHformat. The base station does not provide the UE with information aboutwhere the corresponding PDCCH is in a control region allocated in asubframe. Since the UE cannot know which position its own PDCCH istransmitted at which CCE aggregation level or DCI format in order toreceive a control channel transmitted by the base station, the UEmonitors a set of PDCCH candidates in the subframe and searches its ownPDCCH. This is called blind decoding/detection (BD). The blind decodingrefers to a method, by the UE, for de-masking its own UE identifier (UEID) from a CRC part and then checking whether a corresponding PDCCH isits own control channel by reviewing a CRC error.

In an active mode, the UE monitors a PDCCH of each subframe in order toreceive data transmitted to the UE. In a DRX mode, the UE wakes up in amonitoring interval of each DRX period and monitors a PDCCH in asubframe corresponding to the monitoring interval. A subframe in whichthe monitoring of the PDCCH is performed is called a non-DRX subframe.

The UE shall perform the blind decoding on all of CCEs present in acontrol region of the non-DRX subframe in order to receive the PDCCHtransmitted to the UE. Since the UE does not know which PDCCH formatwill be transmitted, the UE shall decode all of PDCCHs at a possible CCEaggregation level until the blind decoding of the PDCCHs is successfulwithin each non-DRX subframe. Since the UE does not know how many CCEsare used for the PDCCH for the UE, the UE shall attempt detection at allthe possible CCE aggregation levels until the blind decoding of thePDCCH is successful. That is, the UE performs the blind decoding per CCEaggregation level. That is, the UE first attempts decoding by setting aCCE aggregation level unit to 1. If all the decoding fails, the UEattempts decoding by setting the CCE aggregation level unit to 2.Thereafter, the UE attempts decoding by setting the CCE aggregationlevel unit to 4 and setting the CCE aggregation level unit to 8.Furthermore, the UE attempts the blind decoding on a total of four ofC-RNTI, P-RNTI, SI-RNTI, and RA-RNTI. The UE attempts blind decoding onall the DCI formats that need to be monitored.

As described above, if the UE performs blind decoding on all thepossible RNTIs and all the DCI formats, that need to monitored, per eachof all the CCE aggregation levels, the number of detection attemptsexcessively increases. Therefore, in the LTE system, a search space (SS)concept is defined for the blind decoding of the UE. The search spacemeans a set of PDCCH candidates for monitoring, and may have a differentsize depending on each PDCCH format.

The search space may include a common search space (CSS) and aUE-specific/dedicated search space (USS). In the case of the commonsearch space, all the UEs may be aware of the size of the common searchspace, but the UE-specific search space may be individually configuredto each UE. Thus, the UE must monitor both the UE-specific search spaceand the common search space in order to decode the PDCCH, and thusperforms blind decoding (BD) up to 44 times in one subframe. This doesnot include blind decoding performed based on a different CRC value(e.g., C-RNTI, P-RNTI, SI-RNTI, RA-RNTI).

There may occur a case where the base station cannot secure CCEresources for transmitting a PDCCH to all the UEs which intend totransmit the PDCCH within a given subframe due to a small search space.This is because resources left over after a CCE location is allocatedmay not be included in a search space of a specific UE. In order tominimize such a barrier that may continue even in a next subframe, aUE-specific hopping sequence may be applied to the point at which theUE-specific search space starts.

Table 7 represents the size of the common search space and theUE-specific search space.

TABLE 7 Number of Number of candidates candidates PDCCH Number of incommon in dedicated format CCEs (n) search space search space 0 1 — 6 12 — 6 2 4 4 2 3 8 2 2

In order to reduce a computational load of a UE according to the numberof times that the UE attempts blind decoding, the UE does not performsearch according to all of defined DCI formats at the same time.Specifically, the UE may always perform search for DCI formats 0 and 1Ain the UE-specific search space. In this instance, the DCI formats 0 and1A have the same size, but the UE may distinguish between the DCIformats using a flag for the DCI format 0/format 1A differentiationincluded in a PDCCH. Furthermore, DCI formats other than the DCI formats0 and 1A may be required for the UE depending on a PDSCH transmissionmode configured by the base station. For example, DCI formats 1, 1B and2 may be used.

The UE in the common search space may search for the DCI formats 1A and1C. Furthermore, the UE may be configured to search for the DCI format 3or 3A. The DCI formats 3 and 3A have the same size as the DCI formats 0and 1A, but the UE may distinguish between the DCI formats using CRSscrambled by another identifier not a UE-specific identifier.

A search space S_(k) ^((L)) means a set of PDCCH candidates according toan aggregation level L∈{1,2,4,8}. A CCE according to a PDCCH candidateset m of the search space may be determined by the following Equation 3.L·{(Y _(k) +m)mod └N _(CCE,k) /L┘}+i  [Equation 3]

Here, M^((L)) represents the number of PDCCH candidates according to aCCE aggregation level L for monitoring in the search space, and m=0, . .. , M^((L))−1. i is an index for designating an individual CCE in eachPDCCH candidate, where i=0, . . . , L−1.

As described above, the UE monitors both the UE-specific search spaceand the common search space in order to decode the PDCCH. Here, thecommon search space (CSS) supports PDCCHs with an aggregation level of{4, 8}, and the UE-specific search space (US S) supports PDCCHs with anaggregation level of {1, 2, 4, 8}.

Table 8 represents DCCH candidates monitored by a UE.

TABLE 8 Search space S_(k) ^((L)) Number of Aggregation Size PDCCH Typelevel L [in CCEs] candidates M^((L)) UE- 1 6 6 specific 2 12 6 4 8 2 816 2 Common 4 16 4 8 16 2

Referring to Equation 3, in case of the common search space, Y_(k) isset to 0 with respect to two aggregation levels L=4 and L=8. On theother hand, in case of the UE-specific search space with respect to anaggregation level L, Y_(k) is defined as in Equation 4Y _(k)=(A·Y _(k−1))mod D  [Equation 4]

Here, Y⁻¹=n_(RNTI) ≠0, and an RNTI value used for n_(RNTI) may bedefined as one of identifications of the UE. Further, A=39827, D=65537,and k=└n_(s)/2┘ where n_(s) denotes a slot number (or index) in a radioframe.

General ACK/NACK Multiplexing Method

In a situation in which a UE shall simultaneously transmit multipleACKs/NACKs corresponding to multiple data units received from an eNB, anACK/NACK multiplexing method based on PUCCH resource selection may beconsidered to maintain single-frequency characteristics of an ACK/NACKsignal and reduce ACK/NACK transmission power.

Together with ACK/NACK multiplexing, contents of ACK/NACK responses formultiple data units are identified by combining a PUCCH resource and aresource of QPSK modulation symbols used for actual ACK/NACKtransmission.

For example, if one PUCCH resource transmits 4 bits and up to four dataunits can be transmitted, an ACK/NACK result can be identified at theeNB as indicated in the following Table 9.

TABLE 9 HARQ-ACK(0), HARQ-ACK(1), HARQ-ACK(2), b(0), HARQ-ACK(3)n_(PUCCH) ⁽¹⁾ b(1) ACK, ACK, ACK, ACK n_(PUCCH, 1) ⁽¹⁾ 1, 1 ACK, ACK,ACK, NACK/DTX n_(PUCCH, 1) ⁽¹⁾ 1, 0 NACK/DTX, NACK/DTX, NACK, DTXn_(PUCCH, 2) ⁽¹⁾ 1, 1 ACK, ACK, NACK/DTX, ACK n_(PUCCH, 1) ⁽¹⁾ 1, 0NACK, DTX, DTX, DTX n_(PUCCH, 0) ⁽¹⁾ 1, 0 ACK, ACK, NACK/DTX, NACK/DTXn_(PUCCH, 1) ⁽¹⁾ 1, 0 ACK, NACK/DTX, ACK, ACK n_(PUCCH, 3) ⁽¹⁾ 0, 1NACK/DTX, NACK/DTX, NACK/DTX, NACK n_(PUCCH, 3) ⁽¹⁾ 1, 1 ACK, NACK/DTX,ACK, NACK/DTX n_(PUCCH, 2) ⁽¹⁾ 0, 1 ACK, NACK/DTX, NACK/DTX, ACKn_(PUCCH, 0) ⁽¹⁾ 0, 1 ACK, NACK/DTX, NACK/DTX, NACK/DTX n_(PUCCH, 0) ⁽¹⁾1, 1 NACK/DTX, ACK, ACK, ACK n_(PUCCH, 3) ⁽¹⁾ 0, 1 NACK/DTX, NACK, DTX,DTX n_(PUCCH, 1) ⁽¹⁾ 0, 0 NACK/DTX, ACK, ACK, NACK/DTX n_(PUCCH, 2) ⁽¹⁾1, 0 NACK/DTX, ACK, NACK/DTX, ACK n_(PUCCH, 3) ⁽¹⁾ 1, 0 NACK/DTX, ACK,NACK/DTX, NACK/DTX n_(PUCCH, 1) ⁽¹⁾ 0, 1 NACK/DTX, NACK/DTX, ACK, ACKn_(PUCCH, 3) ⁽¹⁾ 0, 1 NACK/DTX, NACK/DTX, ACK, NACK/DTX n_(PUCCH, 2) ⁽¹⁾0, 0 NACK/DTX, NACK/DTX, NACK/DTX, ACK n_(PUCCH, 3) ⁽¹⁾ 0, 0 DTX, DTX,DTX, DTX N/A N/A

In the above Table 9, HARQ-ACK(i) represents an ACK/NACK result for ani-th data unit. In the above Table 9, discontinuous transmission (DTX)means that there is no data unit to be transmitted for the correspondingHARQ-ACK(i) or that the UE does not detect the data unit correspondingto the HARQ-ACK(i). According to the above Table 9, a maximum of fourPUCCH resources (n_(PUCCH,0) ⁽¹⁾, n_(PUCCH,1) ⁽¹⁾, n_(PUCCH,2) ⁽¹⁾, andn_(PUCCH,3) ⁽¹⁾) are provided, and b(0) and b(1) are two bitstransmitted by using a selected PUCCH.

For example, if the UE successfully receives all of four data units, theUE transmits 2-bit (1,1) using n_(PUCCH,1) ⁽¹⁾.

If the UE fails in decoding in first and third data units and succeedsin decoding in second and fourth data units, the US transmits bits (1,0)using n_(PUCCH,3) ⁽¹⁾.

In ACK/NACK channel selection, if there is at least one ACK, the NACKand the DTX are coupled with each other. This is because a combinationof the reserved PUCCH resource and the QPSK symbol may not all ACK/NACKstates. However, if there is no ACK, the DTX is decoupled from the NACK.

In this case, the PUCCH resource linked to the data unit correspondingto one definite NACK may also be reserved to transmit signals ofmultiple ACKs/NACKs.

General ACK/NACK Transmission

In the LTE-A system, it considers to transmit, via a specific ULcomponent carrier (CC), a plurality of ACK/NACK information/signals fora plurality of PDS CHs transmitted via a plurality of DL CCs. To thisend, unlike ACK/NACK transmission using PUCCH format 1a/1b in theexisting Rel-8 LTE, it may consider to transmit a plurality of ACK/NACKinformation/signals by channel-coding (e.g., Reed-Muller code,Tail-biting convolutional code, etc.) a plurality of ACK/NACKinformation and then using PUCCH format 2 or a new PUCCH format (i.e.,E-PUCCH format) of the following block spreading based modified type.

A block spreading scheme is a scheme for modulating control signaltransmission using an SC-FDMA method, unlike the existing PUCCH format 1series or 2 series. As illustrated in FIG. 8 , a symbol sequence may bespread on a time domain using an orthogonal cover code (OCC) and may betransmitted. Control signals of a plurality of UEs may be multiplexed onthe same RB using the OCC. In case of the PUCCH format 2 describedabove, one symbol sequence is transmitted over the time domain, and thecontrol signals of the plurality of UEs are multiplexed using a cyclicshift (CS) of a CAZAC sequence. On the other hand, in case of the blockspreading based PUCCH format (e.g., PUCCH format 3), one symbol sequenceis transmitted over a frequency domain, and the control signals of theplurality of UEs are multiplexed using a time domain spreading using theOCC.

FIG. 16 illustrates an example of generating and transmitting 5 SC-FDMAsymbols during one slot in a wireless communication system to which thepresent invention is applicable.

FIG. 16 illustrates an example of generating and transmitting fiveSC-FDMA symbols (i.e., data part) using an OCC of the length 5 (or SF=5)in one symbol sequence during one slot. In this case, two RS symbols maybe used during one slot.

In the example of FIG. 16 , the RS symbol may be generated from a CAZACsequence, to which a specific cyclic shift value is applied, and may betransmitted in the form in which a predetermined OCC is applied (ormultiplied) over a plurality of RS symbols. Further, in the example ofFIG. 8 , if it is assumed that 12 modulation symbols are used for eachOFDM symbol (or SC-FDMA symbol) and each modulation symbol is generatedby QPSK, the maximum number of bits which can be transmitted on one slotis 24 bits (=12×2). Thus, the number of bits which can be transmitted ontwo slots is a total of 48 bits. If a PUCCH channel structure of theblock spreading scheme is used as described above, control informationof an extended size can be transmitted as compared to the existing PUCCHformat 1 series and 2 series.

For convenience of explanation, such a channel coding based method fortransmitting a plurality of ACKs/NACKs using the PUCCH format 2 or theE-PUCCH format is referred to as a multi-bit ACK/NACK codingtransmission method. The method refers to a method for transmitting anACK/NACK coded block generated by channel-coding ACK/NACK information ordiscontinuous transmission (DTX) information (representing that a PDCCHhas not been received/detected) for PDSCHs of a plurality of DL CCs. Forexample, if the UE operates in a SU-MIMO mode on any DL CC and receivestwo codewords (CWs), the UE may transmit a total of 4 feedback states ofACK/ACK, ACK/NACK, NACK/ACK, and NACK/NACK per CW on the DL CC, or mayhave up to 5 feedback states including until DTX. If the UE receives asingle CW, the UE may have up to 3 states of ACK, NACK, and DTX (if NACKand DTX are identically processed, the UE may have a total of two statesof ACK and NACK/DTX). Thus, if the UE aggregates up to 5 DL CCs andoperates in an SU-MIMO mode on all the CCs, the UE may have up to 55transmittable feedback states, and the size of an ACK/NACK payload forrepresenting these states is a total of 12 bits (if DTX and NACK areidentically processed, the number of feedback states is 45, and the sizeof the ACK/NACK payload for representing these states is a total of 10bits).

In the above ACK/NACK multiplexing (i.e., ACK/NACK selection) methodapplied to the existing Rel-8 TDD system, the method may basicallyconsider an implicit ACK/NACK selection method that uses implicit PUCCHresources (i.e., linked to a lowest CCE index) corresponding to PDCCHscheduling each PDSCH of the corresponding UE, in order to secure PUCCHresources of each UE. The LTE-A FDD system basically considers aplurality of ACK/NACK transmissions for a plurality of PDSCHs, which istransmitted via a plurality of DL CCs, via one specific UL CC that isUE-specifically configured. To this end, the LTE-A FDD system considersan ACK/NACK selection method using an implicit PUCCH resource linked toPDCCH (i.e., linked to a lowest CCE index n_CCE, or linked to n_CCE andn_CCE+1) that schedules a specific DL CC, or some of DL CCs, or all DLCCs, or a combination of the corresponding implicit PUCCH resource andan explicit PUCCH resource that is previously reserved to each UE viaRRC signaling.

The LTE-A TDD system may also consider a situation in which a pluralityof CCs is aggregated (i.e., CA). Hence, it may consider transmitting aplurality of ACK/NACK information/signals for a plurality of PDSCHs,which is transmitted via a plurality of DL subframes and a plurality ofCCs, via a specific CC (i.e., AN/CC) in UL subframes corresponding tothe corresponding plurality of DL subframes. In this instance, unlikethe LTE-A FDD system mentioned above, the LTE-A TDD system may considera method (i.e., full ACK/NACK) for transmitting a plurality ofACKs/NACKs corresponding to the maximum number of CWs, that can betransmitted via all the CCs assigned to the UE, in all of a plurality ofDL subframes (i.e., SFs), or a method (i.e., bundles ACK/NACK) fortransmitting ACKs/NACKs by applying ACK/NACK bundling to CW and/or CCand/or SF domain to reduce the total number of ACKs/NACKs to betransmitted (here, the CW bundling means that ACK/NACK bundling for CWis applied to each DL SF per each CC, the CC bundling means thatACK/NACK bundling for all or some of CCs is applied to each DL SF, andthe SF bundling means that ACK/NACK bundling for all or some of DL SFsis applied to each CC. Characteristically, as a SF bundling method, itmay consider an ACK-counter method which informs the total number ofACKs (or the number of some of the ACKs) per CC with respect to allPDSCHs or DL grant PDCCHs received for each CC). In this instance, amulti-bit ACK/NACK coding or an ACK/NACK selection based ACK/NACKtransmission method may be configurably applied according to a size ofan ACK/NACK payload per UE, i.e., a size of an ACK/NACK payload for fullor bundled ACK/NACK transmission that is configured for each UE.

ACK/NACK Transmission for LTE-A

The LTE-A system supports transmitting, via a specific UL CC, aplurality of ACK/NACK information/signals for a plurality of PDSCHswhich are transmitted via a plurality of DL CCs. To this end, unlikeACK/NACK transmission using PUCCH format 1a/1b in the existing Rel-8LTE, a plurality of ACK/NACK information may be transmitted through aPUCCH format 3.

FIG. 17 illustrates an ACK/NACK channel structure for PUCCH format 3with a normal CP.

As illustrated in FIG. 17 , a symbol sequence is transmitted bytime-domain spreading by an orthogonal cover code (OCC) and maymultiplex control signals of multiple UEs on the same RB using the OCC.In the PUCCH format 2 mentioned above, one symbol sequence istransmitted over a time domain and performs the UE multiplexing using acyclic shift of a CAZAC sequence. On the other hand, in case of thePUCCH format 3, one symbol sequence is transmitted over a frequencydomain and performs the UE multiplexing using the time-domain spreadingbased on the OCC. FIG. 17 illustrates a method for generating andtransmitting five SC-FDMA symbols from one symbol sequence using OCC oflength-5 (spreading factor=5). In an example of FIG. 17 , a total of twoRS symbols have been used during one slot, but various applicationsincluding a method of using three RS symbols and using the OCC ofspreading factor=4, etc. may be considered. Here, the RS symbol may begenerated from a CAZAC sequence with a specific cyclic shift and may betransmitted in the form in which a specific OCC is applied (ormultiplied) to a plurality of RS symbols of the time domain. In theexample of FIG. 17 , if it is assumed that 12 modulation symbols areused for each SC-FDMA symbol and each modulation symbol uses QPSK, themaximum number of bits which can be transmitted on each slot is 24 bits(=12×2). Thus, the number of bits which can be transmitted on two slotsis a total of 48 bits.

For convenience of explanation, such a channel coding based method fortransmitting a plurality of ACKs/NACKs using the PUCCH format 2 or theE-PUCCH format is referred to as a “multi-bit ACK/NACK coding”transmission method. The method refers to a method for transmitting anACK/NACK coded block generated by channel-coding ACK/NACK information orDTX information (representing that a PDCCH has not beenreceived/detected) for PDSCHs of a plurality of DL CCs. For example, ifthe UE operates in a SU-MIMO mode on any DL CC and receives twocodewords (CWs), the UE may transmit a total of 4 feedback states ofACK/ACK, ACK/NACK, NACK/ACK, and NACK/NACK per CW on the DL CC, or mayhave up to 5 feedback states including until DTX. If the UE receives asingle CW, the UE may have up to 3 states of ACK, NACK, and DTX (if NACKand DTX are identically processed, the UE may have a total of two statesof ACK and NACK/DTX). Thus, if the UE aggregates up to 5 DL CCs andoperates in an SU-MIMO mode on all the CCs, the UE may have up to 55transmittable feedback states, and the size of an ACK/NACK payload forrepresenting these states is a total of 12 bits (if DTX and NACK areidentically processed, the number of feedback states is 45, and the sizeof the ACK/NACK payload for representing these states is a total of 10bits).

In the above ACK/NACK multiplexing (i.e., ACK/NACK selection) methodapplied to the existing Rel-8 TDD system, the method may basicallyconsider an implicit ACK/NACK selection method that uses implicit PUCCHresources (i.e., linked to a lowest CCE index) corresponding to PDCCHscheduling each PDSCH of the corresponding UE, in order to secure PUCCHresources of each UE. The LTE-A FDD system basically considers aplurality of ACK/NACK transmissions for a plurality of PDSCHs, which istransmitted via a plurality of DL CCs, via one specific UL CC that isUE-specifically configured. To this end, the LTE-A FDD system considersan “ACK/NACK selection” method using an implicit PUCCH resource linkedto PDCCH (i.e., linked to a lowest CCE index n_CCE, or linked to n_CCEand n_CCE+1) that schedules a specific DL CC, or some of DL CCs, or allDL CCs, or a combination of the corresponding implicit PUCCH resourceand an explicit PUCCH resource that is previously reserved to each UEvia RRC signaling.

The LTE-A TDD system may also consider a situation in which a pluralityof CCs is aggregated (i.e., CA). Hence, it may consider transmitting aplurality of ACK/NACK information/signals for a plurality of PDSCHs,which is transmitted via a plurality of DL subframes and a plurality ofCCs, via a specific CC (i.e., AN/CC) in UL subframes corresponding tothe corresponding plurality of DL subframes. In this instance, unlikethe LTE-A FDD system mentioned above, the LTE-A TDD system may considera method (i.e., full ACK/NACK) for transmitting a plurality ofACKs/NACKs corresponding to the maximum number of CWs, that can betransmitted via all the CCs assigned to the UE, in all of a plurality ofDL subframes (i.e., SFs), or a method (i.e., bundles ACK/NACK) fortransmitting ACKs/NACKs by applying ACK/NACK bundling to CW and/or CCand/or SF domain to reduce the total number of ACKs/NACKs to betransmitted (here, the CW bundling means that ACK/NACK bundling for CWis applied to each DL SF per each CC, the CC bundling means thatACK/NACK bundling for all or some of CCs is applied to each DL SF, andthe SF bundling means that ACK/NACK bundling for all or some of DL SFsis applied to each CC. Characteristically, as a SF bundling method, itmay consider an “ACK-counter” method which informs of the total numberof ACKs (or the number of some ACKs) per CC for all PDSCHs or DL grantPDCCHs received for each CC). In this instance, a “multi-bit ACK/NACKcoding” or an “ACK/NACK selection” based ACK/NACK transmission methodmay be configurably applied according to a size of an ACK/NACK payloadper UE, i.e., a size of an ACK/NACK payload for the full or bundledACK/NACK transmission that is configured for each UE.

The next-generation wireless communication system requires a largefrequency band and aims to support various services or requirements. Asone example, among New Radio (NR) requirements of the 3GPP, UltraReliable and Low Latency Communication (URLLC), one of representativescenarios, may require a low latency and high reliability requirementthat user plane latency is within 0.5 ms and transmission of X bytes isperformed with less than 10⁻⁵ error rate.

Also, in contrast to enhanced Mobile BroadBand (eMBB) which requires alarge traffic capacity, traffic of URLLC is characterized that it occurssporadically and a file size ranges from tens to hundreds of bytes.

Therefore, while eMBB requires that transmission rate is maximized andoverhead of control information is minimized, URLLC requires a shortscheduling time unit and a reliable transmission method.

A reference time unit assumed and/or used for transmission and receptionof a physical channel may be set to various values according to anapplication area or type of traffic. The reference time may be a defaultunit for scheduling a specific physical channel. The reference time unitmay be varied according to the number of symbols constituting thecorresponding scheduling unit and/or subcarrier spacing.

For the convenience of descriptions, the present specification uses aslot and a mini-slot as the reference time unit. For example, a slot maybe the default scheduling unit used for general data traffic (forexample, eMBB).

A mini-slot may have a shorter time interval in the time domain than theslot. A mini-slot may be the default scheduling unit used for morespecial purpose traffic or communication schemes (for example, URLLC,unlicensed band or millimeter wave).

However, the specific assumption above is only an example, and it shouldbe clearly understood that the proposed methods of the presentspecification may be modified and applied even to the case where eMBBtransmits and receives a physical channel by using a mini-slot and/orthe case where URLLC or other communication scheme transmits andreceives a physical channel by using a slot.

In what follows, the present specification reinterprets existing fieldsand proposes a method (hereinafter, a first embodiment) for indicatinginformation related to repetition of a Physical Downlink Shared Channel(PDSCH), a method (hereinafter, a second embodiment) for interpretingCFI according to support for a PDSCH repetition-related operation, amethod (hereinafter, a third embodiment) for determining PUCCH resourcesfor transmitting an HARQ-ACK, a method (hereinafter, a fourthembodiment) for reporting whether PDSCH decoding with respect to aspecific TTI within a predetermined time period is supported, a method(hereinafter, a fifth embodiment) for indicating and/or configuringwhether to report an HARQ-ACK with respect to a PDSCH, a method(hereinafter, a sixth embodiment) for configuring and/or reportingwhether an operation for supporting specific latency and/or reliabilityrequirements is supported, a method (hereinafter, a seventh embodiment)for improving reliability of reception of a PDSCH repetition in theoccurrence of a TTI in which a PDSCH repetition operation is unable totransmit downlink data, and a method (hereinafter, an eighth embodiment)for determining and/or configuring whether to allow DL DMRS sharing in aTTI over a plurality of contiguous subframes.

In what follows, embodiments described in the present specification aredistinguished from each other only in an attempt for the convenience ofdescriptions, and it should be clearly understood that part of a methodand/or structure of a particular embodiment may be substituted by amethod and/or structure of another embodiment or may be applied in acombination thereof.

Also, in what follows, terms like slot, subframe, and frame used in theembodiments described in the present specification may correspond tospecific examples of particular time units used in a wirelesscommunication system. In other words, in applying the methods proposedin the present specification, the time unit may be replaced with adifferent time unit applied to another wireless communication system.

First Embodiment

Now, described will be a method for indicating information related torepetition of a Physical Downlink Shared Channel (PDSCH) byreinterpreting existing fields.

To improve transmission reliability of a PDSCH, a method fortransmitting the same transport block (TB) repeatedly over a pluralityof Transmission Time Intervals (TTIs) instead of transmitting a HybridAutomatic Repeat and request-Acknowledgement (HARQ-ACK) (namely,blind/HARQ-less PDSCH repetition) may be considered. The repetition ofthe same TB may be scheduled by indicating the number of repetitions inthe Downlink Control Information (DCI). Similarly, repetition of thesame TB may be scheduled by configuring the number of repetitionsthrough higher layer signaling. Further, the repetition of the same TBmay be scheduled by using the same HARQ process ID and/or non-toggledNew Data Indicator (NDI) with respect to (contiguous) TTIs or TTIs(within predetermined time duration).

The transmission performance of a PDSCH may depend on how accurately aPDCCH is decoded. This is so because, if decoding of a PDCCH fails, itis also actually impossible to decode a PDSCH that schedules thedecoding of a PDCCH.

To perform the repetition operation, a method for adding a DCI field maybe taken into account. However, it may not be preferable since themethod increases the payload of a PDCCH and as a result, PDCCD decodingperformance may be degraded. Therefore, to avoid degradation of PDCCHdecoding performance and/or avoid attempting additional blind decoding(BD), it may be preferable to maintain an existing DCI format size.

Therefore, as an example, a rule may be defined, agreed on and/orconfigured so that whether to repeat the PDSCH and/or informationrelated to the number of repetitions may be indicated by using thefields such as HARQ process ID, Redundancy Version (RV), NDI, TransmitPower Control (TPC) command, Downlink Assignment Index (DAI) and/orAcknowledgement Resource Indicator (ARI). In other words, a rule may bedefined, agreed on and/or configured so that part of the fields arereinterpreted to indicate whether to repeat the PDSCH and/or informationrelated to the number of repetitions without addition of a field to theexisting DCI format and/or without size change (and/or without anadditional BD configuration with respect to the existing BD). Here,reinterpretation may mean interpreting a specific field value as a valuerelated to whether to repeat the PDSCH and/or the number of repetitionsof the PDSCH.

Here, HARQ process ID, RV, NDI, TPC command, DAI and/or ARI are thefields related to HARQ feedback. If a low latency requirement is 1 ms,it is not necessary to consider HARQ-ACK feedback (namely,retransmission by the HARQ-ACK feedback), it may be possible toreinterpret the fields and use the interpretation result to indicateanother information. Whether the UE has to perform the operation ofreinterpreting the specific field(s) and indicating whether to repeatthe PDSCH and/or information related to the number of repetitions of thePDSCH may be configured through a higher layer signal. Or, a rule may bedefined, agreed on and/or configured so that part of the specific fieldsis reinterpreted to indicate whether to repeat the PDSCH and/orinformation related to the number of repetitions only when ablind/HARQ-less PDSCH repetition operation is enabled through higherlayer signaling.

And/or, a rule may be defined, agreed on and/or configured so that partof the fields is reinterpreted to indicate information related tointer-TTI hopping of a PDSCH being repeated without addition of a fieldto the existing DCI format and/or without size change (and/or without anadditional BD configuration with respect to the existing BD). Frequencydiversity gain may be expected through inter-TTI hopping. Also, throughthe frequency diversity gain, the decoding performance of a PDSCH beingrepeated may be further improved.

If an operation of reinterpreting part of the fields and indicatinginformation related to inter-TTI hopping of a PDSCH being repeatedwithout addition of a field to the existing DCI format and/or withoutsize change (and/or without an additional BD configuration with respectto the existing BD) is performed, whether the corresponding operationhas to be performed may be configured for the UE through higher layersignaling. Or, a rule may be defined, agreed on and/or configured sothat part of the fields may be reinterpreted to indicate informationrelated to inter-TTI hopping of a PDSCH being repeated only when ablind/HARQ-less PDSCH repetition operation is enabled through higherlayer signaling. Here, the information related to inter-TTI hopping isan example, which may indicate (pattern/offset) information related towhich frequency resource to be used for each TTI when the same TB istransmitted repeatedly to a plurality of TTIs.

And/or, if the inter-TTI hopping operation of a PDSCH is configuredand/or indicated, a field indicating DMRS sharing may be reinterpreted.If the inter-TTI hopping operation of a PDSCH being repeated isconfigured and/or indicated, the DMRS sharing operation may not bepreferable. This is so because, while a plurality of TTIs for which DMRSsharing is to be applied have to use at least the same precodingresource block group (PRG), the hopping operation for obtaining thefrequency diversity gain has to use different frequency resources asmuch as possible. Therefore, if an inter-TTI hopping operation of aPDSCH being repeated is configured and/or indicated, a rule may bedefined, agreed on and/or configured so that a field indicating DMRSsharing is reinterpreted to indicate whether to repeat the PDSCH and/orinformation related to the number of repetitions and/or informationrelated to inter-TTI hopping of a PDSCH being repeated.

Second Embodiment

In what follows, described will be a method for interpreting CFIaccording to whether a PDSCH repetition-related operation is enabled.

Reliability of URLLC transmission and reception may be affected byreliability of a control channel, which may be greatly influenced inparticular by decoding performance of a Physical Control FormatIndicator Channel (PCFICH). In case a UE wrongly decodes a PCFICH andrecognizes a control channel area (for example, the number of symbolsoccupied by the control channel) incorrectly, reliability of the controlchannel may be adversely affected, and (in the case of a subslotoperation) the UE may recognize a downlink (DL) TTI boundary in a waydifferent from how a base station (BS) understands the DL TTI boundaryand perform decoding accordingly. To prevent this operation, a methodfor configuring information about a control channel area for a UEthrough higher layer signaling is under consideration.

Therefore, a UE may determine whether to adopt a control formatindicator (CFI) value based on a PCFICH or whether to adopt a CFI valuethrough higher layer signaling by using the method described in thefollowing.

The methods described below are divided only for the convenience ofdescriptions, and it should be clearly understood that a structure of aparticular method may be substituted by a structure of another method ormay be applied in a combination thereof

(Method 1)

If a higher layer signal defines whether to enable the blind/HARQ-lessPDSCH (or HARQ-less and/or blind PDSCH) repetition operation, and/or ifsupport for an operation for indicating whether to repeat a PDSCH and/orinformation related to the number of repetitions throughreinterpretation of a specific field of the existing DCI format asdescribed in the first embodiment is defined, agreed on and/orconfigured by a higher layer signal, and/or if support for an operationfor indicating information related to inter-TTI hopping of a PDSCH beingrepeated through reinterpretation of a specific field is defined, agreedon and/or configured by a higher layer signal, a UE may accordinglydetermine whether to adopt a CFI value based on a PCFICH or whether toadopt a CFI value configured through a higher layer signal. In otherwords, a rule may be defined in such a way that in case ablind/HARQ-less PDSCH repetition operation is enabled through higherlayer signaling, the UE uses a CFI value configured through higher layersignaling but uses a CFI value based on a PCFICH, otherwise.

(Method 2)

If an operation for indicating whether to repeat a PDSCH and/orinformation related to the number of repetitions throughreinterpretation of a specific field of the existing DCI format by ahigher layer signal is enabled, a rule may be defined so that a UE usesa CFI value configured through a higher layer signal but uses a CFIvalue based on a PCFICH, otherwise.

(Method 3)

A UE may interpret a CFI value differently for cases where the number ofrepetitions is smaller than a predetermined value and for the remainingcases. If the number of repetitions is high, it means that a largernumber of repetitions are required, which may be interpreted thatchannel conditions are not good; in this case, it may be better for theUE to use a value preconfigured by a higher layer signal as the CFIvalue rather than depend on PCFICH decoding. Therefore, a rule may bedefined so that the UE uses a CFI value based on the PCFICH when thenumber of PDSCH repetitions is smaller than a predetermined value butuses a CFI value configured through higher layer signaling when it islarger than a predetermined value.

(Method 4)

A rule may be defined so that in case an operation for indicatinginformation related to inter-TTI hopping of a PDSCH being repeatedthrough reinterpretation of a specific field of the existing DCI formatby a higher layer signal is enabled, a UE uses a CFI value configuredthrough the higher layer signal and otherwise uses a CFI value based ona PCFICH.

(Method 5)

A rule may be defined so that in reducing payload of DCI to be less thana conventional payload to improve reliability of a PDCCH (namely, inintroducing compact DCI), a UE uses a CFI value configured through anhigher layer signal within a TTI configured for monitoring of the DCIformat or within a subframe including the corresponding TTI while the UEuses a CFI value based on a PCFICH within a TTI not configured formonitoring of the DCI format or within a subframe including the TTI.

Third Embodiment

Now, a method for determining PUCCH resources for transmitting HARQ-ACKwill be described.

In case the ARI field of the existing DCI format is reinterpreted toindicate whether to repeat and/or information related to the number ofrepetitions or information related to inter-TTI hopping, a UE mayencounter ambiguity in determining HARQ-ACK resources.

To prevent the ambiguity, a rule may be defined, agreed on and/orconfigured as described below.

The methods described below are divided only for the convenience ofdescriptions, and it should be clearly understood that a structure of aparticular method may be substituted by a structure of another method ormay be applied in a combination thereof

(Method 1)

A rule may be defined, agreed on and/or configured so that in case theARI field of the existing DCI format is reinterpreted to indicatewhether to repeat and/or information related to the number ofrepetitions or information related to inter-TTI hopping, the UEtransmits HARQ-ACK by using a PUCCH resource defined separately inadvance.

(Method 2)

A rule may be defined, agreed on and/or configured so that in case theARI field of the existing DCI format is reinterpreted to indicatewhether to repeat and/or information related to the number ofrepetitions or information related to inter-TTI hopping, the UE uses aresource agreed on in advance among PUCCH resources associated with therespective states of the ARI field (for example, associated with thefirst state or associated with the first state among resourcesconfigured with a specific PUCCH format).

(Method 3)

A rule may be defined, agreed on and/or configured so that in case theARI field of the existing DCI format is reinterpreted to indicatewhether to repeat and/or information related to the number ofrepetitions or information related to inter-TTI hopping, the UE uses aPUCCH resource associated with a specific Control Channel Element (CCE)(for example, lowest CCE index).

And/or a rule may be defined, agreed on and/or configured so that incase the TPC field of the existing DCI format is reinterpreted toindicate whether to repeat and/or information related to the number ofrepetitions or information related to inter-TTI hopping, a TPC commandis considered to be 0 dB (namely no adjustment). And/or a rule may bedefined, agreed on and/or configured so that in case accumulation due toa TPC command is not enabled, a value agreed on in advance and/or apreconfigured, specific absolute power value is applied.

Fourth Embodiment

In what follows, described will be a method for reporting whether PDSCHdecoding with respect to a specific TTI within time duration ispossible.

Suppose a UE is capable of performing PDSCH decoding with respect to aspecific TTI within specific time duration in a situation where a datachannel is transmitted repeatedly over a plurality of TTIs with respectto the same TB described in the first embodiment. If decoding issuccessfully performed, the UE's processing of a data channeltransmitted repeatedly in the subsequent TTIs may not be needed (or notuseful). Therefore, power saving may be expected as the UE skipsprocesses after the decoding is done successfully.

In other words, a rule may be defined, agreed on and/or configured sothat whether PDSCH decoding may be performed with respect to a specificTTI within time duration is defined as capability of a UE, and the UEcapability is reported to a base station (or network).

Here, “time duration” may correspond to a time period from the time atwhich a PDSCH is received until the next TTI (or the corresponding TTIafter a predefined/preconfigured amount of time) with respect to thePDSCH transmitted repeatedly. Or, the time duration may correspond to atime period from the time at which a PDSCH is received until receptionof a scheduling PDCCH with respect to the PDSCH transmitted repeatedly.The time duration may be predefined or indicated together when the UEreports its capability. And/or, if a plurality of time duration isdefined and/or indicated, the UE may independently report whether PDSCHdecoding may be performed with respect to a specific TTI in each of theplurality of time duration.

And/or, according to the capability of performing PDSCH decoding withrespect to a specific TTI within time duration and/or configuration of abase station with respect to the corresponding operation, the HARQ-ACKtransmission operation of a UE may be determined differently. Supposethe UE is capable of performing PDSCH decoding with respect to aspecific TTI within time duration or the corresponding operation isconfigured. If PDSCH decoding is performed successfully, the UE mayperform HARQ-ACK feedback at a timing after a predefined and/orpreconfigured processing time from the time of successful reception ofthe PDSCH and may not be requested to perform decoding of the PDSCHtransmitted repeatedly afterwards. Also, the UE may not be requested toperform buffering and/or combining with respect to the PDSCH transmittedrepeatedly afterwards and may not be requested to perform HARQ-ACKtransmission with respect to the PDSCH transmitted repeatedlyafterwards. Meanwhile, a rule may be defined, agreed on and/orconfigured so that a UE without the capability or not configured for thecorresponding operation performs HARQ-ACK feedback corresponding to thelast PDSCH reception TTI after combining the PDSCH transmittedrepeatedly in a plurality of TTIs.

And/or, according to the UE's capability of combining a PDSCHtransmitted repeatedly and/or configuration of a base station withrespect to the corresponding operation, the HARQ-ACK transmissionoperation of the UE may be determined differently. A rule may bedefined, agreed on and/or configured so that a UE supporting combiningor configured for combining performs HARQ-ACK feedback corresponding tothe last PDSCH reception TTI after performing combining of the PDSCHtransmitted repeatedly in a plurality of TTIs while a UE not supportingcombining nor configured for combining performs separately HARQ-ACKfeedback corresponding to each PDSCH received in each of the pluralityof TTIs.

Fifth Element

Described will be a method for indicating and/or configuring whether toreport HARQ-ACK with respect to a PDSCH.

Whether to enable an operation (for example, blind/HARQ-less PDSCHrepetition) for supporting specific latency and/or reliabilityrequirement may be configured through an higher layer signal. And/or,support for latency and/or reliability requirement itself may beconfigured through a higher layer signal. A UE configured for thesupport may not have to perform retransmission and/or HARQ-ACK reportdepending on the latency requirement.

When it is assumed that whether a PDSCH is repeated and/or the number ofrepetitions is indicated dynamically to the UE, it may not be preferableto determine whether to report HARQ-ACK through a higher layer signal.As one example, this is so because even if blind/HARQ-less PDSCHrepetition is configured through a higher layer signal to supportspecific latency and/or reliability requirement, a base station doesn'thave to support the corresponding latency and/or reliability requirementdepending on the type of traffic but may request a retransmissionoperation without repetition and/or through HARQ-ACK.

Therefore, a rule may be defined, agreed on and/or configured so that aphysical layer signal indicates whether a UE should report an HARQ-ACKwith respect to a specific PDSCH.

The rule may be such that it is applied only to the case where anoperation for supporting specific latency and/or reliability requirement(for example, blind/HARQ-less PDSCH repetition) is made possible througha higher layer signal. A rule may be defined, agreed on and/orconfigured so that in case the dynamic indication indicates an HARQ-ACKreport, the UE reports an HARQ-ACK with respect to a repetition bundleof the PDSCH or reports an HARQ-ACK with respect to the whole (or part)of individual PDSCHs corresponding to the repetition bundle. Meanwhile,a rule may be defined, agreed on and/or configured so that in case thedynamic indication indicates not to report an HARQ-ACK, the UE decodes arepetition bundle of the PDSCH but does not report an HARQ-ACK.

Whether to report the HARQ-ACK may be indicated and/or configured by anexplicitly added bit field (for example, a dynamic indication field). Inthis case, too, the operation for supporting specific latency and/orreliability requirement (for example, blind/HARQ-less repetition of thePDSCH) is made possible through a higher layer signal.

And/or, whether to report the HARQ-ACK may be determined byreinterpretation of the existing DCI field.

And/or, whether to report the HARQ-ACK may be determined by the numberof PDSCH repetitions. As one example, a rule may be defined, agreed onand/or configured so that in case the number of repetitions is smallerthan a predetermined value, the UE reports an HARQ-ACK with respect tothe repetition bundle or reports an HARQ-ACK with respect to the whole(or part) of individual PDSCHs corresponding to the repetition bundle.Meanwhile, a rule may be defined, agreed on and/or configured so that ifthe number of repetitions exceeds the predetermined value, the UEdecodes the repetition bundle of the PDSCH but does not report theHARQ-ACK.

Sixth Embodiment

In what follows, described in detail will be a method for configuringand/or reporting whether to enable an operation for supporting specificlatency and/or reliability requirement.

Whether to enable an operation for supporting specific latency and/orreliability requirement (for example, blind/HARQ-less PDSCH (orHARQ-less and/or blind PDSCH) repetition and/or UL semi-persistentscheduling (SPS) with repetition) may be configured through a higherlayer signal. Also, whether to enable the operation may be configuredindependently for each TTI length or each combination of DL and UL TTIlengths. Or, whether to enable the operation may be defined(differently) independently for each frame structure and so configuredfor a UE.

And/or, information about whether to enable an operation for supportingspecific latency and/or reliability requirement (for example,blind/HARQ-less PDSCH repetition and/or UL SPS with repetition) (in howmany carrier components (CCs) and/or cells) may be defined as UEcapability and reported to the base station (or network).

The information may be reported separately for each TTI length (group)or for each combination (group) of DL and UL TTI lengths. As oneexample, the UE capability may be defined separately for each subslot,slot, and subframe or for each combination of {DL=subslot, UL=subslot},{DL=subslot, UL=slot}, {DL=slot, UL=slot}, and {DL=subframe,UL=subframe}.

Or, the UE capability may be defined (differently) separately for eachframe structure and reported to the base station (or network). Or, theUE capability may be defined separately for each band and/or each bandcombination.

And/or if the UE reports the UE capability, the base station maydetermine to which degree the UE supports the operation based on the UEcapability and configure and/or operate so that the reported operationand/or a specific operation of the reported operation may be supported.For example, a specific operation may include an operation ofinterpreting a DCI field differently to add a specific field to theexisting DCI format, a BD operation with respect to a DCI monitoringmethod/the number of BD or specific DCI format, an operation forreceiving and/or decoding of a PDSCH transmitted repeatedly, and anHARQ-ACK transmission operation with respect to the last PDSCH among thereceived and/or decoded PDSCHs.

In particular, a rule may be defined, agreed on and/or configured sothat the UE capability, which indicates whether an operation forsupporting the specific latency and/or reliability requirement (forexample, blind/HARQ-less PDSCH repetition and/or repeated UL SPS) isenabled (in how many carrier components and/or cells), is defined andreported only for a UE supporting an operation of configuring the numberof symbols of a control region (of a specific cell) through a higherlayer signal and receiving downlink (DL) control and data based on theconfigured number of symbols.

In other words, for the case of a UE not supporting an operation ofconfiguring the number of symbols of a control region (of a specificcell) through a higher layer signal and receiving downlink (DL) controland data based on the configured number of symbols, the operation forsupporting the specific latency and/or reliability requirement (forexample, blind/HARQ-less PDSCH repetition and/or repeated UL SPS) maynot always be supported, either.

Meanwhile, for the case of a UE not supporting an operation ofconfiguring the number of symbols of a control region (of a specificcell) through a higher layer signal and receiving downlink (DL) controland data based on the configured number of symbols, whether theoperation for supporting the specific latency and/or reliabilityrequirement (for example, blind/HARQ-less PDSCH repetition and/orrepeated UL SPS) is supported may be reported through capabilitysignaling.

Through the method above, a UE is allowed to support PDSCH repetitiononly for the case where the UE supports configuration of the number ofsymbols of a semi-static control region through a higher layer signal,thereby improving reception reliability of the PDSCH repetition.

Also, in the case of a data repetition operation in the existing MTC, itmay be known in advance whether to count as soon as a UE receives an RRCsetup in a semi-static situation. However, the present disclosure isdifferent in that a repetition operation is performed according toreceived CFI irrespective of a semi-static situation. Therefore, thepresent disclosure may confirm an invalid TTI dynamically and receiveand/or decode a PDSCH even if the invalid TTI is different in eachsubframe, thereby improving reception reliability of the PDSCHrepetition.

Seventh Embodiment

First, described will be a method for improving reception reliability ofPDSCH repetition in the occurrence of a TTI in which the PDSCHrepetition operation is unable to transmit downlink data.

In case whether to enable a blind/HARQ-less PDSCH (or HARQ-less and/orblind PDSCH) repetition operation is defined, agreed on and/orconfigured by a higher layer signal, information related to the numberof repetitions of a Physical Downlink Shared Channel (PDSCH) (forexample, repetition number) may be indicated and/or transmitted by abase station to a UE through a physical layer signal. The UE may knowfor how many TTIs the PDSCH is transmitted repeatedly with respect tothe same transport block (TB) based on the information about the numberof repetitions and perform a reception operation. For example, theinformation related to the number of repetitions may be a total numberof Transmission Time intervals (TTIs) for PDSCH repetitions scheduled bythe corresponding PDCCH, including the TTI at the time of receiving thePDCCH.

In case the first short TTI within a subframe (for example, subslot #0)is unable to transmit downlink (DL) data (namely, in case the PDSCH maynot be transmitted to the subslot #0) according to the Control FormatIndicator (CFI) value configured through a Physical Control FormatIndicator Channel (PCFICH) or a higher layer signal, the UE mayinterpret the TTIs in which repeated transmission of an actual PDSCH isperformed differently from how the base station interprets the TTIsaccording to whether the corresponding TTI (for example, subslot) isincluded in the total number of transmission TTIs for PDSCH repetitionsindicated by the information related to the number of repetitions. Here,“#number” may denote the index. For example, subslot #0 may denote asubslot with an index of 0 within a subframe.

As one example, as shown in FIG. 18(a), as many PDSCHs as the totalnumber of transmission TTIs for PDSCH repetitions may be transmittedwhile subslot #0 1811 to which the PDSCH may not be transmitted isexcluded and/or skipped over. Similarly, as shown in FIG. 18(b), as manyPDSCHs as the total number of transmission TTIs for PDSCH repetitionsmay be transmitted by including even subslot #0 1821 to which the PDSCHmay not be transmitted. Interpretations as given above may degradereception reliability of the PDSCH between an base station and a UE.

Therefore, a rule may be defined, agreed on and/or configured so that incase whether to enable a blind/HARQ-less PDSCH repetition operation isdefined by a higher layer signal, a UE assumes the number oftransmissions (TTIs) of a PDSCH corresponding to repeated transmissionas in the following methods to perform PDSCH decoding.

The methods described below are divided only for the convenience ofdescriptions, and it should be clearly understood that a structure of aparticular method may be substituted by a structure of another method ormay be applied in a combination thereof

(Method 1)

If a control region configured and/or indicated through a higher layersignal and/or physical layer signal consists of two or three OFDMsymbols, the UE excludes and/or skips the corresponding TTI (forexample, subslot #0) or TTIs affected by the length of the controlregion (for example, subslot #0 and subslot #1) and performs decoding byassuming that as many PDSCHs as the total number of transmission TTIsfor configured and/or indicated PDSCH repetitions are transmitted. Forexample, as shown in FIG. 18(a), the UE may perform decoding by takinginto account that the PDSCH has been transmitted repeatedly with subslot#0 1811 being skipped over.

(Method 2)

If a control region configured and/or indicated through a higher layersignal and/or physical layer signal consists of one OFDM symbol, the UEperforms decoding by assuming that as many PDSCHs as the total number oftransmission TTIs for configured and/or indicated PDSCH repetitionsincluding the corresponding TTI (for example, subslot #0) or a TTIaffected by the length of the control region (for example, subslot #0and subslot #1) are transmitted. For example, as shown in FIG. 18(b),the UE may perform decoding as if the PDSCH has been transmittedrepeatedly including subslot #0 1821.

(Method 3)

The UE may perform decoding by always excluding and/or skipping thecorresponding TTI (for example, subslot #0) regardless of the number ofsymbols of the control region and by assuming that as many PDSCHs as thetotal number of transmission TTIs for configured and/or indicated PDSCHrepetitions are transmitted.

(Method 4)

A rule may be defined, agreed on and/or configured so that a PDSCHrepetition operation is limited within subframe boundaries and a UEperforms decoding of PDSCHs transmitted repeatedly over a plurality ofTTIs with respect to the same TB only within a subframe. In other words,a UE may not expect decoding of PDSCHs transmitted repeatedly in aplurality of TTIs with respect to the same TB over a plurality ofcontiguous subframes.

(Method 5)

A UE may determine TTIs in which a PDSCH transmitted repeatedlyaccording to a method for indicating the number of symbols of a downlink(DL) control region with respect to a specific carrier and/or cell (forexample, a physical layer signal (PCFICH) or higher layer signal) isreceived. If the number of symbols of the control region is indicated bya PCFICH, performance of a control channel may be determined by thePCFICH decoding performance of the UE. Also, in determining a subslotpattern, the boundary between subslot #0 and subslot #1 may be wronglydetermined, which leads to degradation of downlink data channel decodingperformance.

Therefore, in case the number of symbols of a control region (of aspecific cell) is indicated by the PCFICH, the UE may always excludeand/or skip a TTI within the control region (for example, subslot #0) orTTIs affected by the length of the control region (for example, subslot#0 and subslot #1) and perform decoding by assuming that the PDSCH isactually transmitted as many times as the total number of transmissionTTIs for configured and/or indicated PDSCH repetitions. Meanwhile, incase the number of symbols of a control region (of a specific cell) isconfigured through a higher layer signal, if the control region consistsof two or three OFDM symbols according to the configured number ofsymbols of the control region, the UE excludes and/or skips a TTI withinthe control region (for example, subslot #0) and performs decoding byassuming that the PDSCH is actually transmitted as many times as thetotal number of transmission TTIs for configured and/or indicated PDSCHrepetitions while, if the control region consists of one OFDM symbols,the UE includes a TTI within the control region (for example, subslot#0) and performs decoding by assuming that the PDSCH is actuallytransmitted as many times as the total number of transmission TTIs forconfigured and/or indicated PDSCH repetitions.

In the present specification, the control region may indicate the numberof OFDM symbols used for PDCCH transmission within a subframe. Also, thecontrol region may be determined by the information indicated to the UEthrough a physical layer signal (for example, PCFICH) and/or higherlayer signal (for example, RRC message).

Eighth Embodiment

Before the eighth embodiment is described, the structure of a radioframe is first described. In FIG. 1(a), a subframe using Δf=15 kHz maybe further divided into six subslots according to Table 10 below.

TABLE 10 Subslot number 0 1 2 3 4 5 Slot number 2i 2i + 1 Uplink subslotpattern 0, 1, 2 3, 4 5, 6 0, 1 2, 3 4, 5, 6 Downlink subslot pattern 10, 1, 2 3, 4 5, 6 0, 1 2, 3 4, 5, 6 Downlink subslot pattern 2 0, 1, 2,3, 4 5, 6 0, 1 2, 3 4, 5, 6

In the case of FDD, 10 subframes, 20 slots, or a maximum of 60 subslotsmay be used for downlink transmission at 10 ms intervals while 10subframes, 20 slots, or a maximum of 60 subslots may be used for uplinktransmission at 10 ms intervals. Uplink and downlink transmission may beseparated from each other in the frequency domain. In a half-duplex FDDoperation, a UE is unable to perform transmission and receptionsimultaneously. On the other hand, in a full-duplex FDD operation, theUE is capable of performing transmission and reception simultaneously.

Next, described will be a method for determining and/or configuringwhether to allow DL Demodulation Reference Signal (DMRS) sharing withrespect to a TTI over a plurality of contiguous subframes.

In the case of a subslot-PDSCH, DMRS sharing may be allowed for thepurpose of reducing overhead due to DMRS. A rule is defined that toprevent performance degradation of channel estimation, DMRS sharing isallowed only between two subslots and taking into account the processingtime of a UE, the corresponding DMRS is mapped to the preceding one ofthe two subslots at the time of DMRS sharing. According to a predefinedrule (for example, 3GPP specification), if a UE fails to detect downlink(DL) assignment short downlink control information (sDCI) at subslot#n−1 and the downlink assignment sDCI detected at subslot #n indicatesabsence of DMRS in the subslot #n, the UE does not expect decoding ofsubslot-PDSCH in the subslot #n.

Whether to allow DL DMRS sharing with respect to a TTI over a pluralityof contiguous subframes may be determined by the following method.

The methods described below are divided only for the convenience ofdescriptions, and it should be clearly understood that a structure of aparticular method may be substituted by a structure of another method ormay be applied in a combination thereof

(Method 1)

A rule may be defined, agreed on and/or configured so that whether toallow the DL DMRS sharing operation for a TTI over a plurality ofcontiguous subframes is determined differently according to the numberof symbols of a control region configured and/or indicated through ahigher layer signal and/or physical layer signal.

As one example, if a control region configured and/or indicated througha higher layer signal and/or physical layer signal consists of one OFDMsymbol, the DL DMRS sharing operation may be allowed, applied,configured and/or indicated with respect to a TTI over a plurality ofcontiguous subframes. Meanwhile, if a control region configured and/orindicated through a higher layer signal and/or physical layer signalconsists of two or three OFDM symbols, the DL DMRS sharing operation maynot be allowed, applied, configured and/or indicated with respect to aTTI over a plurality of contiguous subframes. In this case, the UE mayreceive a DMRS with respect to each individual TTI.

(Method 2)

A rule may be defined, agreed on and/or configured so that whether theDL DMRS sharing operation is allowed, applied, configured, and/orindicated with respect to a TTI over a plurality of contiguous subframesis determined according to whether the number of symbols of a controlregion with respect to the length of the corresponding TTI is configuredthrough a higher layer signal or indicated by a physical layer signal(for example, PCFICH). As one example, if the number of symbols of acontrol region is configured through a higher layer signal, whether toallow, apply, configure and/or indicate the DL DMRS may be determined bythe number of symbols of a control region configured according to themethod 1. On the other hand, if the number of symbols of a controlregion is indicated by a physical layer signal (for example, PCFICH),the UE may not expect DL DMRS sharing to be allowed, applied,configured, and/or indicated.

Since examples of the embodiments proposed in the present specificationmay also be included as implementation methods of the presentdisclosure, it is obvious that the examples may be regarded as a kind ofembodiments.

Also, as described above, although embodiments proposed by the presentspecification may be implemented independently, they may still beimplemented in the form of a combination (merge) of part of embodiments.A rule may be defined, agreed on and/or configured so that a basestation provides information about whether to apply embodiments (orinformation about rules of the embodiments) to a UE through predefinedsignaling (for example, physical layer signaling and/or higher layersignaling).

FIG. 19 is a flow diagram illustrating an operation method of a UEaccording to the present specification.

Referring to FIG. 19 , first, a user equipment (UE) may transmit, to abase station (BS), capability information including the firstinformation indicating support for a PDSCH repetition-related operationS1901.

The PDSCH repetition-related operation may be an HARQ-less/blind (orHARQ-less and/or blind) PDSCH repetition operation.

The first information may include information indicating whether tosupport repetition for each Transmission Time Interval (TTI) length orinformation indicating whether to support repetition of one or morespecific TTI lengths.

For example, the first information may include information indicatingwhether to support repetition of subframes, information indicatingwhether to support repetition of slots, and/or information indicatingwhether to support repetition of subslots. As a specific example,information indicating support for subframe repetition may betransmitted to a base station through a higher layer parameterpdsch-RepSubframe and/or pdsch-RepSubframe-r15. Information indicatingsupport for slot repetition may be transmitted to the BS through ahigher layer parameter pdsch-RepSlot. Information indicating support forsubslot repetition may be transmitted to the BS through a higher layerparameter pdsch-RepSubSlot.

Also, the capability information may further include informationindicating whether configuration of the number of symbols of a controlregion through the higher layer signal is supported (for example,semiStaticCFI-r15 or semiStaticCFI-Pattern-r15). For example, the basestation may receive information indicating support for configuration ofthe number of symbols of the control region and when configuration ofthe number of symbols of the control region is supported, may transmitinformation about the number of symbols of the control region to the UEthrough a higher layer signal. At this time, the UE may ignoreinformation about the number of symbols of the control region comingthrough the PCFICH channel but receive information about the number ofsymbols of the control region through a higher layer signal to receiveand/or decode control information.

Also, the first information may be transmitted when configuration of thenumber of symbols of a control region through a higher layer signal issupported (for example, semiStaticCFI-r15 or semiStaticCFI-Pattern-r15).Here, the first information may be the information indicating supportfor subframe repetition.

In other words, the subframe repetition may be supported whenconfiguration of the number of symbols of a control region through ahigher layer signal (for example, semiStaticCFI-SlotSubslotNonMBSFN,semiStaticCFI-SlotSubslotMBSFN, semiStaticCFI-SubframeNonMBSFN, orsemiStaticCFI-SubframeMBSFN) is supported.

And/or, the first information may include information about support forrepetition for each DL and UL TTI length combination or informationabout support for repetition of a combination of one or more specificTTI lengths. For example, the first information may include informationabout support for each of uplink TTI length combination 1 {DL=subslot,UL=subslot}, uplink TTI length combination 2 {DL=subslot, UL=slot},uplink TTI length combination 3 {DL=slot, UL=slot}, and uplink TTIlength combination 4 {DL=subframe, UL=subframe}.

And/or the first information may include information indicating supportfor repetition for each frame structure or information indicatingsupport for repetition of one or more specific frame structures.

And/or the first information may include information indicating supportfor repetition for each band and/or each band combination or informationindicating support for repetition of one or more specific bands and/orband combination.

Next, the UE may receive the second information for configuring whetherto enable the PDSCH repetition-related operation and/or informationabout the number of symbols of a control region from the BS through ahigher layer signal S1902. The BS may transmit, to the UE, the secondinformation and/or information about the number of symbols of thecontrol region based on the capability information. For example, thesecond information may be transmitted to the UE through a higher layerparameter blindSlotSubslotPDSCH-Repetitions and/orblindSubframePDSCH-Repetitions. Also, the information about the numberof symbols of a control region may be transmitted to the UE through ahigher layer parameter semiStaticCFI-SlotSubslotNonMBSFN,semiStaticCFI-SlotSubslotMBSFN, semiStaticCFI-SubframeNonMBSFN, orsemiStaticCFI-SubframeMBSFN.

Next, when the second information is configured as enable, the UE mayreceive, from the BS, downlink control information (DCI) related toreception of a PDSCH repetition S1903. For example, the UE may check thenumber of symbols of DCI based on the information about the number ofsymbols of a control region and receive the DCI. The DCI related toreception of a PDSCH repetition may include information about the numberof repetitions of the PDSCH (for example, Repetition number).

Next, the UE may receive the PDSCH repeatedly from the BS based on theDCI S1904. The UE may receive the PDSCH repeatedly based on theinformation about the number of repetitions.

In what follows, since the operation method of a UE illustrated in FIG.19 is the same as the operation method of a UE described with referenceto FIGS. 1 to 18 , detailed descriptions of the remaining part thereofwill be omitted.

Related to the method, operation of a UE described in detail above maybe implemented specifically by the UE device 2120 described withreference to FIG. 21 . For example, operation of the UE described abovemay be performed by the processor 2121 and/or RF unit 2123.

Referring to FIG. 21 , first, the processor 2121 may transmit capabilityinformation including the first information indicating support for aPDSCH repetition-related operation to a base station through the RF unit2123, S1901.

The PDSCH repetition-related operation may be an HARQ-less/blind (orHARQ-less and/or blind) PDSCH repetition operation.

The first information may include information indicating whether tosupport repetition for each Transmission Time Interval (TTI) length orinformation indicating whether to support repetition of one or morespecific TTI lengths.

For example, the first information may include information indicatingwhether to support repetition of subframes, information indicatingwhether to support repetition of slots, and/or information indicatingwhether to support repetition of subslots. As a specific example,information indicating support for subframe repetition may betransmitted to a BS through a higher layer parameter pdsch-RepSubframeand/or pdsch-RepSubframe-r15. Information indicating support for slotrepetition may be transmitted to the BS through a higher layer parameterpdsch-RepSlot. Information indicating support for subslot repetition maybe transmitted to the BS through a higher layer parameterpdsch-RepSubSlot.

Also, the capability information may further include informationindicating whether configuration of the number of symbols of a controlregion through the higher layer signal is supported (for example,semiStaticCFI-r15 or semiStaticCFI-Pattern-r15). For example, the BS mayreceive information indicating support for configuration of the numberof symbols of the control region and when configuration of the number ofsymbols of the control region is supported, may transmit informationabout the number of symbols of the control region to the UE through ahigher layer signal. At this time, the UE may ignore information aboutthe number of symbols of the control region coming through the PCFICHchannel but receive information about the number of symbols of thecontrol region through a higher layer signal to receive and/or decodecontrol information.

Also, the first information may be transmitted when configuration of thenumber of symbols of a control region through a higher layer signal issupported (for example, semiStaticCFI-r15 or semiStaticCFI-Pattern-r15).Here, the first information may be the information indicating supportfor subframe repetition.

In other words, the subframe repetition may be supported whenconfiguration of the number of symbols of a control region through ahigher layer signal (for example, semiStaticCFI-SlotSubslotNonMBSFN,semiStaticCFI-SlotSubslotMBSFN, semiStaticCFI-SubframeNonMBSFN, orsemiStaticCFI-SubframeMBSFN) is supported.

And/or, the first information may include information about support forrepetition for each DL and UL TTI length combination or informationabout support for repetition of a combination of one or more specificTTI lengths. For example, the first information may include informationabout support for each of uplink TTI length combination 1 {DL=subslot,UL=subslot}, uplink TTI length combination 2 {DL=subslot, UL=slot},uplink TTI length combination 3 {DL=slot, UL=slot}, and uplink TTIlength combination 4 {DL=subframe, UL=subframe}.

And/or the first information may include information indicating supportfor repetition for each frame structure or information indicatingsupport for repetition of one or more specific frame structures.

And/or the first information may include information indicating supportfor repetition for each band and/or each band combination or informationindicating support for repetition of one or more specific bands and/orband combination.

Next, the processor 2121 may receive the second information forconfiguring whether to enable the PDSCH repetition-related operationand/or information about the number of symbols of a control region fromthe BS via the RF unit 2123 through a higher layer signal S1902. The BSmay transmit, to the UE, the second information and/or information aboutthe number of symbols of the control region based on the capabilityinformation. For example, the second information may be transmitted tothe UE through a higher layer parameterblindSlotSubslotPDSCH-Repetitions and/or blindSubframePDSCH-Repetitions.Also, the information about the number of symbols of a control regionmay be transmitted to the UE through a higher layer parametersemiStaticCFI-SlotSubslotNonMBSFN, semiStaticCFI-SlotSubslotMBSFN,semiStaticCFI-SubframeNonMBSFN, or semiStaticCFI-SubframeMBSFN.

Next, when the second information is configured as enable, the processor2121 may receive, from the BS, downlink control information (DCI)related to reception of a PDSCH repetition via the RF unit 2123, S1903.For example, the UE may check the number of symbols of DCI based on theinformation about the number of symbols of a control region and receivethe DCI. The DCI related to reception of a PDSCH repetition may includeinformation about the number of repetitions of the PDSCH (for example,Repetition number).

Next, the processor 2121 may receive the PDSCH repeatedly from the BSbased on the DCI via the RF unit 2123, S1904. The UE may receive thePDSCH repeatedly based on the information about the number ofrepetitions.

In what follows, since the operation method of a UE illustrated in FIG.21 is the same as the operation method of a UE described with referenceto FIGS. 1 to 20 , detailed descriptions of the remaining part thereofwill be omitted.

FIG. 20 is a flow diagram illustrating an operation method of a basestation according to the present specification.

Referring to FIG. 20 , first, a base station (BS) may receive capabilityinformation including the first information indicating support for aPDSCH repetition-related operation from a user equipment (UE) S2001.

The PDSCH repetition-related operation may be an HARQ-less/blind (orHARQ-less and/or blind) PDSCH repetition operation.

The first information may include information indicating whether tosupport repetition for each Transmission Time Interval (TTI) length orinformation indicating whether to support repetition of one or morespecific TTI lengths.

For example, the first information may include information indicatingwhether to support repetition of subframes, information indicatingwhether to support repetition of slots, and/or information indicatingwhether to support repetition of subslots. As a specific example,information indicating support for subframe repetition may betransmitted to a base station (BS) through a higher layer parameterpdsch-RepSubframe and/or pdsch-RepSubframe-r15. Information indicatingsupport for slot repetition may be transmitted to the BS through ahigher layer parameter pdsch-RepSlot. Information indicating support forsubslot repetition may be transmitted to the BS through a higher layerparameter pdsch-RepSubSlot.

Also, the capability information may further include informationindicating whether configuration of the number of symbols of a controlregion through the higher layer signal is supported (for example,semiStaticCFI-r15 or semiStaticCFI-Pattern-r15).

Also, the first information may be received by the BS when the UEsupports configuration of the number of symbols of a control regionthrough a higher layer signal (for example, semiStaticCFI-r15 orsemiStaticCFI-Pattern-r15). Here, the first information may be theinformation indicating support for subframe repetition.

In other words, the subframe repetition may be supported when the UEsupports configuration of the number of symbols of a control regionthrough a higher layer signal (for example,semiStaticCFI-SlotSubslotNonMBSFN, semiStaticCFI-SlotSubslotMBSFN,semiStaticCFI-SubframeNonMBSFN, or semiStaticCFI-SubframeMBSFN).

And/or, the first information may include information about support forrepetition for each DL and UL TTI length combination or informationabout support for repetition of a combination of one or more specificTTI lengths. For example, the first information may include informationabout support for each of uplink TTI length combination 1 {DL=subslot,UL=subslot}, uplink TTI length combination 2 {DL=subslot, UL=slot},uplink TTI length combination 3 {DL=slot, UL=slot}, and uplink TTIlength combination 4 {DL=subframe, UL=subframe}.

And/or the first information may include information indicating supportfor repetition for each frame structure or information indicatingsupport for repetition of one or more specific frame structures.

And/or the first information may include information indicating supportfor repetition for each band and/or each band combination or informationindicating support for repetition of one or more specific bands and/orband combination.

Next, the BS may transmit, to the UE, a higher layer signal includingthe second information for configuring whether to enable the blind PDSCHrepetition-related operation and/or information about the number ofsymbols of a control region S2002. The BS may transmit, to the UE, thesecond information and/or information about the number of symbols of thecontrol region based on the capability information. For example, thesecond information may be transmitted to the UE through a higher layerparameter blindSlotSubslotPDS CH-Repetitions and/or blindSubframePDSCH-Repetitions. Also, the information about the number of symbols of acontrol region may be transmitted to the UE through a higher layerparameter semiStaticCFI-SlotSubslotNonMBSFN,semiStaticCFI-SlotSubslotMBSFN, semiStaticCFI-SubframeNonMBSFN, orsemiStaticCFI-SubframeMBSFN.

Next, when the second information is configured as enable, the BS maytransmit, to the BS, downlink control information (DCI) related toreception of a PDSCH repetition S2003. For example, the UE may check thenumber of symbols of DCI based on the information about the number ofsymbols of a control region and receive the DCI. The DCI related toreception of a PDS CH repetition may include information about thenumber of repetitions of the PDS CH (for example, Repetition number).

Next, the BS may transmit the PDSCH repeatedly to the UE S2004. The UEmay receive the PDSCH repeatedly based on the information about thenumber of repetitions.

In what follows, since the operation method of a BS illustrated in FIG.20 is the same as the operation method of a BS described with referenceto FIGS. 1 to 20 , detailed descriptions of the remaining part thereofwill be omitted.

Related to the method, operation of a BS described in detail above maybe implemented specifically by the BS device 2110 described withreference to FIG. 21 . For example, operation of the base stationdescribed above may be performed by the processor 2111 and/or RF unit2113.

Referring to FIG. 21 , first, the processor 2111 may transmit capabilityinformation including the first information indicating support for aPDSCH repetition-related operation to a base station through the RF unit2113, S2001.

The PDSCH repetition-related operation may be an HARQ-less/blind (orHARQ-less and/or blind) PDSCH repetition operation.

The first information may include information indicating whether tosupport repetition for each Transmission Time Interval (TTI) length orinformation indicating whether to support repetition of one or morespecific TTI lengths.

For example, the first information may include information indicatingwhether to support repetition of subframes, information indicatingwhether to support repetition of slots, and/or information indicatingwhether to support repetition of subslots. As a specific example,information indicating support for subframe repetition may betransmitted to a base station through a higher layer parameterpdsch-RepSubframe and/or pdsch-RepSubframe-r15. Information indicatingsupport for slot repetition may be transmitted to the BS through ahigher layer parameter pdsch-RepSlot. Information indicating support forsubslot repetition may be transmitted to the BS through a higher layerparameter pdsch-RepSubSlot.

Also, the capability information may further include informationindicating whether configuration of the number of symbols of a controlregion through the higher layer signal is supported (for example,semiStaticCFI-r15 or semiStaticCFI-Pattern-r15).

Also, the first information may be received by the base station when theUE supports configuration of the number of symbols of a control regionthrough a higher layer signal (for example, semiStaticCFI-r15 orsemiStaticCFI-Pattern-r15). Here, the first information may be theinformation indicating support for subframe repetition.

In other words, the subframe repetition may be supported when the UEsupports configuration of the number of symbols of a control regionthrough a higher layer signal (for example,semiStaticCFI-SlotSubslotNonMBSFN, semiStaticCFI-SlotSubslotMBSFN,semiStaticCFI-SubframeNonMBSFN, or semiStaticCFI-SubframeMBSFN).

And/or, the first information may include information about support forrepetition for each DL and UL TTI length combination or informationabout support for repetition of a combination of one or more specificTTI lengths. For example, the first information may include informationabout support for each of uplink TTI length combination 1 {DL=subslot,UL=subslot}, uplink TTI length combination 2 {DL=subslot, UL=slot},uplink TTI length combination 3 {DL=slot, UL=slot}, and uplink TTIlength combination 4 {DL=subframe, UL=subframe}.

And/or the first information may include information indicating supportfor repetition for each frame structure or information indicatingsupport for repetition of one or more specific frame structures.

And/or the first information may include information indicating supportfor repetition for each band and/or each band combination or informationindicating support for repetition of one or more specific bands and/orband combination.

Next, the processor 2111 may transmit, to the UE, a higher layer signalincluding the second information for configuring whether to enable theblind PDSCH repetition-related operation and/or information about thenumber of symbols of a control region via the RF unit 2113, S2002. TheBS may transmit, to the UE, the second information and/or informationabout the number of symbols of the control region based on thecapability information. For example, the second information may betransmitted to the UE through a higher layer parameterblindSlotSubslotPDSCH-Repetitions and/or blindSubframePDSCH-Repetitions.Also, the information about the number of symbols of a control regionmay be transmitted to the UE through a higher layer parametersemiStaticCFI-SlotSubslotNonMBSFN, semiStaticCFI-SlotSubslotMBSFN,semiStaticCFI-SubframeNonMBSFN, or semiStaticCFI-SubframeMBSFN.

Next, when the second information is configured as enable, the processor2111 may transmit, to the UE, downlink control information (DCI) relatedto reception of a PDSCH repetition through the RF unit 2113, S2003. Forexample, the UE may check the number of symbols of DCI based on theinformation about the number of symbols of a control region and receivethe DCI. The DCI related to reception of a PDSCH repetition may includeinformation about the number of repetitions of the PDSCH (for example,Repetition number).

Next, the processor 2111 may transmit the PDSCH repeatedly to the UEthrough the RF unit 2113, S2004. The UE may receive the PDSCH repeatedlybased on the information about the number of repetitions.

In what follows, since the operation of a BS illustrated in FIG. 21 isthe same as the operation of a BS described with reference to FIGS. 1 to20 , detailed descriptions of the remaining part thereof will beomitted.

Device in General to which the Present Invention May be Applied

FIG. 21 illustrates a block diagram of a wireless communication deviceto which methods proposed in the present specification may be applied.

Referring to FIG. 21 , a wireless communication system comprises a basestation (BS) 2110 and a plurality of UEs 2120 located within the rangeof the BS 2110.

The BS 2110 comprises a processor 2111, memory 2112, and RF (RadioFrequency) unit 2113. The processor 2111 implements the functions,processes and/or methods described with reference to FIGS. 1 to 20 .Layers of a wireless interface protocol may be implemented by theprocessor 2111. The memory 2112, being connected to the processor 2111,stores various kinds of information to operate the processor 2111. TheRF unit 2113, being connected to the processor 2111, transmits and/orreceives a radio signal.

The UE 2120 comprises a processor 2121, memory 2122, and RF unit 2123.The processor 2121 implements the functions, processes and/or methodsdescribed with reference to FIGS. 1 to 20 . Layers of a wirelessinterface protocol may be implemented by the processor 2121. The memory2122, being connected to the processor 2121, stores various kinds ofinformation to operate the processor 2121. The RF unit 2123, beingconnected to the processor 2121, transmits and/or receives a radiosignal.

The memory 2112, 2122 may be installed inside or outside the processor2111, 2121 and may be connected to the processor 2111, 2121 via variouswell-known means.

Also, the BS 2110 and/or the UE 2120 may be equipped with a singleantenna or multiple antennas.

FIG. 22 illustrates a block diagram of a communication device accordingto one embodiment of the present disclosure.

In particular, FIG. 22 illustrates the UE of FIG. 21 in more detail.

Referring to FIG. 22 , the UE may comprise a processor (or digitalsignal processor (DSP)) 2210, RF module (or RF unit) 2235, powermanagement module 2205, antenna 2240, battery 2255, display 2215, keypad2220, memory 2230, Subscriber Identification Module (SIM) card 2225(this configuration is optional), speaker 2245, and microphone 2250. TheUE may also include a single antenna or multiple antennas.

The processor 2210 implements the functions, processes and/or methodsdescribed with reference to FIGS. 1 to 21 . Layers of a wirelessinterface protocol may be implemented by the processor 2210.

The memory 2230, being connected to the processor 2210, stores variouskinds of information to operate the processor 2210. The memory 2230 maybe installed inside or outside the processor 2210 and may be connectedto the processor 2210 via various well-known means.

The user enters command information such as a phone number by pushing(or touching) buttons of the keypad 2220 or by voice activation usingthe microphone 2250. The processor 2210 receives the command informationand performs an appropriate function such as dialing the phone number.Operational data may be extracted from the SIM card 2225 or memory 2230.Also, the processor 2210 may display the command information oroperational information on the display 2215 to support user'srecognition and for the convenience of the user.

The RF module 2235, being connected to the processor 2210, transmitsand/or receives an RF signal. The processor 2210 delivers commandinformation to the RF module 2235 to initiate communication, forexample, to transmit a radio signal comprising voice communication data.The RF module 2235 comprises a receiver and a transmitter to receive andtransmit a radio signal. The antenna 2240 performs a function oftransmitting and receiving a radio signal. When receiving a radiosignal, the RF module 2235 may deliver the signal to be processed by theprocessor 2210 and convert the signal into the baseband. The processedsignal may be converted to audible signal output through the speaker2245 or readable information.

FIG. 23 illustrates one example of an RF module of a wirelesscommunication device to which methods proposed in the presentspecification may be applied.

More specifically, FIG. 23 illustrates one example of an RF module thatmay be implemented in a Frequency Division Duplex (FDD) system.

First, along the transmission path, the processor described withreference to FIGS. 21 and 22 processes data to be transmitted andprovides an analog output signal to the transmitter 2310.

Inside the transmitter 2310, an analog output signal is filtered by alow pass filter (LPF) 2311 to remove images caused by digital-to-analogconversion (ADC), transformed from the baseband up to an RF band by themixer 2312, and amplified by a variable gain amplifier (VGA) 2313. Theamplified signal is filtered by the filter 2314 and is further amplifiedby the power amplifier (PA) 2315, routed via duplexer(s) 2350/antennaswitch(es) 2360, and transmitted through the antenna 2370.

Also, along the reception path, an antenna receives signals from theoutside and provides the received signals, where these signals arerouted via an antenna switch(es) 2360/duplexer(s) 2350 and are providedto the receiver 2320.

Inside the receiver 2320, received signals are amplified by a low noiseamplifier (LNA) 2323 and filtered by a band-pass filter 232. Thefiltered signals are transformed from the RF band down to the basebandby a mixer 2325.

The down-converted signals are filtered by the low-pass filter (LPF)2326 and are amplified by the VGA 2327, after which analog input signalsare obtained to be provided to the processor described with reference toFIGS. 21 and 22 .

Also, the local oscillator (LO) generator 2340 generates transmissionand reception LO signals and provide the generated LO signals to theup-converter 2312 and down-converter 2325, respectively.

Also, the phase locked loop (PLL) 2330 receives control information fromthe processor to generate transmission and reception LO signals atappropriate frequencies and provides control signals to the LO generator2340.

Also, the circuits shown in FIG. 23 may be arranged differently from theway the structure of FIG. 23 is arranged.

FIG. 24 illustrates another example of an RF module of a wirelesscommunication device to which methods proposed in the presentspecification may be applied.

More specifically, FIG. 24 illustrates one example of an RF module thatmay be implemented in a Time Division Duplex (TDD) system.

The transmitter 2410 and the receiver 2420 of an RF module in the TDDsystem have the same structure as that of the transmitter and thereceiver of the RF module of the FDD system.

In what follows, the RF module of the TDD system will be described withrespect only to the structure that differs from that of the RF module ofthe FDD system, and descriptions of FIG. 23 should be consulted for thesame part of the structure.

A signal amplified by a power amplifier (PA) 2415 of the transmitter isrouted via a band select switch 2450, band-pass filter (BPF) 2460, andantenna switch(es) 2470 and is transmitted through an antenna 2480.

Also, along the reception path, the antenna receives signals from theoutside and provide the received signals, where these signals are routedvia an antenna switch(es) 2470, band-pass filter 2460, and band selectswitch 2450 and are provided to the receiver 2420.

The embodiments described above are implemented by combinations ofcomponents and features of the present invention in predetermined forms.Each component or feature should be considered selectively unlessspecified separately. Each component or feature may be carried outwithout being combined with another component or feature. Moreover, somecomponents and/or features are combined with each other and canimplement embodiments of the present invention. The order of operationsdescribed in embodiments of the present invention may be changed. Somecomponents or features of one embodiment may be included in anotherembodiment, or may be replaced by corresponding components or featuresof another embodiment. It is apparent that some claims referring tospecific claims may be combined with another claims referring to theclaims other than the specific claims to constitute the embodiment oradd new claims by means of amendment after the application is filed.

Embodiments of the present invention can be implemented by variousmeans, for example, hardware, firmware, software, or combinationsthereof. When embodiments are implemented by hardware, one embodiment ofthe present invention can be implemented by one or more applicationspecific integrated circuits (ASICs), digital signal processors (DSPs),digital signal processing devices (DSPDs), programmable logic devices(PLDs), field programmable gate arrays (FPGAs), processors, controllers,microcontrollers, microprocessors, and the like.

When embodiments are implemented by firmware or software, one embodimentof the present invention can be implemented by modules, procedures,functions, etc. performing functions or operations described above.Software code can be stored in a memory and can be driven by aprocessor. The memory is provided inside or outside the processor andcan exchange data with the processor by various well-known means.

It is apparent to those skilled in the art that the present inventioncan be embodied in other specific forms without departing from essentialfeatures of the present invention. Accordingly, the aforementioneddetailed description should not be construed as limiting in all aspectsand should be considered as illustrative. The scope of the presentinvention should be determined by rational construing of the appendedclaims, and all modifications within an equivalent scope of the presentinvention are included in the scope of the present invention.

INDUSTRIAL APPLICABILITY

Although a method for transmitting and receiving downlink data in awireless communication system according to the present specification hasbeen described focusing on examples applying to the 3GPP LTE/LTE-Asystem, it can be applied to various wireless communication systems suchas the 5G system other than the 3GPP LTE/LTE-A system.

What is claimed:
 1. A method of receiving, by a user equipment (UE), aPhysical Downlink Shared Channel (PDSCH) in a wireless communicationsystem, the method comprising: transmitting, to a base station (BS),capability information including first information indicating whether tosupport an operation related to a PDSCH repetition and, secondinformation indicating whether to support a configuration of a controlformat indicator (CFI) related to a size of a control region; receivinginformation for enabling an operation related to a blind PDSCHrepetition via a higher layer signaling; receiving configurationinformation for the CFI via a higher layer signaling; receiving, basedon the configuration information for enabling the operation, DownlinkControl Information (DCI) related to the PDSCH repetition number; andrepeatedly receiving, from the BS, the PDSCH based on the DCI, whereinthe first information includes i) information indicating whether tosupport a subframe-based PDSCH repetition, ii) information indicatingwhether to support a slot-based PDSCH repetition, and/or iii)information indicating whether to support a subslot-based PDSCHrepetition, and wherein the UE is capable of at least one of i) thesubframe-based PDSCH repetition, ii) the slot-based PDSCH repetition oriii) the subslot-based PDSCH repetition, based on the configuration ofthe CFI being supported.
 2. A user equipment (UE) configured to receivea Physical Downlink Shared Channel (PDSCH) in a wireless communicationsystem, the UE comprising: at least one transceiver transmitting andreceiving a wireless signal; and at least one processor functionallyconnected to the at least one transceiver, wherein the at least oneprocessor controls to: transmit, to a base station (BS), capabilityinformation including first information indicating whether to support anoperation related to a PDSCH repetition and, second informationindicating whether to support a configuration of a control formatindicator (CFI) related to a size of a control region; receiveinformation for enabling an operation related to a blind PDSCHrepetition via a higher layer signaling; receive configurationinformation for the CFI via a higher layer signaling; receive, based onthe configuration information for enabling the operation, DownlinkControl Information (DCI) related to the PDSCH repetition number; andrepeatedly receive, from the BS, the PDSCH based on the DCI, wherein thefirst information includes i) information indicating whether to supporta subframe-based PDSCH repetition, ii) information indicating whether tosupport a slot-based PDSCH repetition, and/or iii) informationindicating whether to support a subslot-based PDSCH repetition, andwherein the UE is capable of at least one of i) the subframe-based PDSCHrepetition, ii) the slot-based PDSCH repetition or iii) thesubslot-based PDSCH repetition, based on the configuration of the CFIbeing supported.
 3. A method of transmitting, by a base station (BS), aPhysical Downlink Shared Channel (PDSCH) in a wireless communicationsystem, the method comprising: receiving, from a user equipment (UE),capability information including first information indicating whether tosupport an operation related to a PDSCH repetition and, secondinformation indicating whether to support a configuration of a controlformat indicator (CFI) related to a size of a control region;transmitting information for enabling an operation related to a blindPDSCH repetition via a higher layer signaling; transmittingconfiguration information for the CFI via a higher layer signaling;transmitting, based on the configuration information for enabling theoperation Control Information (DCI) related to the PDSCH repetitionnumber; and repeatedly transmitting the PDSCH to the UE, wherein thefirst information includes i) information indicating whether to supporta subframe-based PDSCH repetition, ii) information indicating whether tosupport a slot-based PDSCH repetition, and/or iii) informationindicating whether to support a subslot-based PDSCH repetition, andwherein the UE is capable of at least one of i) the subframe-based PDSCHrepetition, ii) the slot-based PDSCH repetition or iii) thesubslot-based PDSCH repetition, based on the configuration of the CFIbeing supported.
 4. A base station (B S) configured to transmit aPhysical Downlink Shared Channel (PDSCH) in a wireless communicationsystem, the BS comprising: at least one transceiver transmitting andreceiving a wireless signal; and at least one processor functionallyconnected to the at least one transceiver, wherein the at least oneprocessor controls to: receive, from a user equipment (UE), capabilityinformation including first information indicating whether to support anoperation related to a PDSCH repetition and, second informationindicating whether to support a configuration of a control formatindicator (CFI) related to a size of a control region; transmitinformation for enabling an operation related to a blind PDSCHrepetition via a higher layer signaling; transmit configurationinformation for the CFI via a higher layer signaling; transmit, based onthe configuration information for enabling the operation, DownlinkControl Information (DCI) related to the PDSCH repetition number; andrepeatedly transmit the PDSCH to the UE, wherein the first informationincludes i) information indicating whether to support a subframe-basedPDSCH repetition, ii) information indicating whether to support aslot-based PDSCH repetition, and/or iii) information indicating whetherto support a subslot-based PDSCH repetition, and wherein the UE iscapable of at least one of i) the subframe-based PDSCH repetition, ii)the slot-based PDSCH repetition or iii) the subslot-based PDSCHrepetition, based on the configuration of the CFI being supported.